- Email: [email protected]
Individual plasma ghrelin changes in the same patients in hyperthyroid, hypothyroid and euthyroid state
ARTICLE IN PRESS
G Model PEP 69100 1–4
Peptides xxx (2013) xxx–xxx
Contents lists available at ScienceDirect
Peptides journal homepage: www.elsevier.com/locate/peptides
Individual plasma ghrelin changes in the same patients in hyperthyroid, hypothyroid and euthyroid state
1
2
3 4 5 6
Q1
Marek Ruchala a,1 , Edyta Gurgul a,∗,1 , Adam Stangierski a , Elzbieta Wrotkowska a , Jerzy Moczko b,2 a b
Department of Endocrinology, Metabolism and Internal Medicine, Poznan Medical University, 49 Przybyszewskiego St., 60-355 Poznan, Poland Department of Computer Science and Statistics, Poznan Medical University, 79 Dabrowskiego St., 60-529 Poznan, Poland
7
8
a r t i c l e
i n f o
a b s t r a c t
9 10 11 12 13
Article history: Received 2 September 2013 Received in revised form 21 October 2013 Accepted 21 October 2013 Available online xxx
14
20
Keywords: Ghrelin Hyperthyroidism Hypothyroidism Thyroid dysfunction Metabolism
21
1. Introduction
15 16 17 18 19
22 23 24 25 26 27 28 29 30 31 32 33 34
Ghrelin is a multifunctional peptide of widespread expression. Since it has been shown to influence energy homeostatis, its potential role in thyroid dysfunction may have clinical significance. In this study, plasma ghrelin changes have been analyzed in the same patients in three different thyroid states for the first time. The study group consisted of 16 patients who had been diagnosed with hyperthyroidism, were treated with radioiodine, developed hypothyroidism after treatment, and finally became euthyroid on lthyroxine substitution. In the initial state of hyperthyroidism plasma ghrelin levels correlated negatively with fT3 and fT4 . In hypothyroidism ghrelin concentration increased significantly (p < 0.05). Although the mean value of plasma ghrelin tended to decrease in the euthyroid state, the individual difference between hypothyroidism and euthyroidism was not significant. Plasma ghrelin in euthyroidism was still significantly higher than in hyperthyroidism (p < 0.05), and correlated positively with ghrelin levels in hyperthyroidism and hypothyroidism. In our opinion, plasma ghrelin fluctuations may reflect metabolic changes in patients with thyroid dysfunction. Moreover, it cannot be excluded that in thyroid disorders ghrelin acts as a compensatory factor, helping to balance metabolic disturbances. © 2013 Elsevier Inc. All rights reserved.
Ghrelin is a multifunctional peptide that was discovered in 1999 as the first natural ligand for the growth hormone – secretagogue receptor (GHS-R) [22]. GHS-R has two subtypes: GHS-R1a – a functional ghrelin receptor and GHS-R1b, whose role still needs to be analyzed [15,18]. A unique modification (n-octanoylation at Ser 3) enables acylated ghrelin to bind GHS-R1a and exert biological activity [17,22]. Des-acyl ghrelin was previously considered to be inactive, but recent studies have demonstrated that it may also have a biological function [9,11]. Ghrelin is produced mainly in neuroendocrine cells (X/A cells) of the gastric mucosa [3]. However, to a lesser extent, it is also secreted in the intestine, hypothalamus, pituitary and many other tissues [15,40].
Abbreviations: BMI, body mass index; EDTA, ethylenediaminetetraacetic acid; fT3 , free triiodothyronine; fT4 , free thyroxine; GHS-R, growth hormone – secretagogue receptor; NIS, sodium/iodide symporter; RIA, radioimmunoassay; TSH, thyrotropin. ∗ Corresponding author. Tel.: +48 618691330; fax: +48 618691682. E-mail address: [email protected] (E. Gurgul). 1 These authors contributed equally to this work. 2 Tel.: +48 61 854 68 08; fax: +48 61 854 68 08.
Ghrelin was initially described as the first endogenous growth hormone secretagogue, and proved to be a strong stimulator of growth hormone release [36]. Furthermore, it has been described as an essential regulator of metabolic processes, as it increases food intake, acts as an adipogenic factor, stimulates gastric emptying and reduces energy expenditure [35,43,44]. As a result, ghrelin causes energy saving effects, positive energy balance and weight gain [21]. Ghrelin secretion is regulated mainly by the metabolic state. Its plasma concentration is high during fasting and decreases in response to food intake [7]. Similarly, long-term negative energy balance states (anorexia, cachexia) increase ghrelin production while obesity, on the other hand, decreases ghrelin secretion [12,37,42]. It is well known that thyroid hormones play an important role in energy homeostasis. They increase the metabolic rate, thermogenesis and energy expenditure. Thus, hyperthyroidism as a hypermetabolic state is associated with increased appetite, but also with increased energy expenditure and weight loss. In contrast, hypothyroid patients present a decreased metabolic rate and weight gain. The presence of ghrelin receptors has been demonstrated in the thyroid [5,15,27,40]. Furthermore, exogenous ghrelin uptake in thyroid tissue has been shown to be notably high in rats [32]. Previous studies have revealed that in hyperthyroidism plasma ghrelin levels are decreased [1,4,10,13,16,23,30,31,38,39] and rise
0196-9781/$ – see front matter © 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.peptides.2013.10.018
Please cite this article in press as: Ruchala M, et al. Individual plasma ghrelin changes in the same patients in hyperthyroid, hypothyroid and euthyroid state. Peptides (2013), http://dx.doi.org/10.1016/j.peptides.2013.10.018
35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59
G Model PEP 69100 1–4
ARTICLE IN PRESS M. Ruchala et al. / Peptides xxx (2013) xxx–xxx
2
80
after treatment [10,13,30,31,38,39]. These observations were surprising in view of such symptoms as increased appetite and weight loss in hyperthyroid patients. Hypothyroidism has been predominantly associated with a high ghrelin level [4,14,23] that decreases after treatment [14]. Some authors did not notice any difference [13,33,38], or observed low plasma ghrelin levels in hypothyroid patients [2]. To the best of our knowledge, none of the previous studies evaluated plasma ghrelin concentrations in three different thyroid functional states in the same patients. Various individual factors influence plasma ghrelin levels, i.e. metabolic rate, kidney function, or lipoprotein concentration [8,42,45]. Thus, it seems that a comparison of three different groups of hyper-, hypo- and euthyroid patients may not always be accurately objective. Consequently, the aim of the study was to evaluate the fluctuations of plasma ghrelin concentrations in the same patients during their hyperthyroid, hypothyroid and euthyroid state. We assume that such an analysis may help to understand the dynamic changes of ghrelin concentration based only on the thyroid state at a given time, without the interference of other individual features.
81
2. Materials and methods
82
2.1. Study group
60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79
91
The study group consisted of 16 patients who had been diagnosed with hyperthyroidism (13 women and 3 men), were treated with radioiodine, developed hypothyroidism after treatment, and finally became euthyroid on l-thyroxine substitution. Plasma ghrelin concentration was assessed in these patients during the hyperthyroid, hypothyroid and euthyroid state. Blood samples were collected after a 10-h overnight fast and placed in polyethylene tubes containing plasma enzymes inhibitors (aprotinin and ethylenediaminetetraacetic acid – EDTA).
92
2.2. Laboratory methods
83 84 85 86 87 88 89 90
93 94 95 96 97 98 99 100
101
Total plasma ghrelin levels were measured in duplicate with a commercially available radioimmunoassay (RIA) (Phoenix Pharmaceuticals Inc.). Radioactivity of the samples was assessed in an automatic LKB-Wallace gamma counter. The technique of plasma ghrelin measurement has been already described [24]. Free thyroxine (fT4 ), free triiodothyronine (fT3 ) and thyrotropin (TSH) levels were assessed using an electrochemiluminescence method. 2.3. Statistical methods
105
Plasma ghrelin changes in the hyperthyroid, hypothyroid and euthyroid state were analyzed using the non-parametric Friedman test, and the post hoc multiple comparison tests. Correlations were assessed with the use of Spearman’s rank correlation coefficient.
106
2.4. Ethics
102 103 104
108
The study was conducted with the permission of Poznan University of Medical Sciences Ethical Committee.
109
3. Results
107
110 111 112 113
In the initial state of hyperthyroidism plasma ghrelin level (ghrelin 1) (160.1 ± 90.5 pg/ml) correlated negatively with fT3 (r = −0.67, p < 0.05) and fT4 (r = −0.83, p < 0.05). In hypothyroidism (ghrelin 2) (364.6 ± 269.4 pg/ml) it increased considerably (p < 0.05)
Fig. 1. Individual plasma ghrelin changes in each patient. Plasma ghrelin levels evaluated in hyperthyroidism, hypothyroidism and euthyroidism.
(Fig. 1). Although the mean value of plasma ghrelin concentration tended to decrease when the patients achieved euthyroidism, the individual difference between hypothyroidism (ghrelin 2) and euthyroidism (ghrelin 3) (251.8 ± 132.9 pg/ml) was not significant. Plasma ghrelin in euthyroidism was still significantly higher than in the initial state of hyperthyroidism (p < 0.05) and correlated positively with plasma ghrelin concentrations measured in hyperthyroidism (r = 0.65, p < 0.05) and hypothyroidism (r = 0.93, p < 0.05). At the moment of submitting this manuscript two patients were still characterized by increased TSH levels (5.9 IU/ml and 5.1 IU/ml). However, they presented a major clinical improvement and notable decrease of TSH concentrations in comparison to the hypothyroid state (hypothyroid TSH 59.9 IU/ml and 50.81 IU/ml, respectively). One patient was evaluated during hyperthyroidism, then in euthyroidism after radioiodine treatment, and finally in hypothyroidism that developed afterwards (Table 1). 4. Discussion
115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131
132
In our study, in the initial state of hyperthyroidism plasma ghrelin levels correlated negatively with free thyroid hormones (fT3 and fT4 ). Hyperthyroid patients presented a low ghrelin level, which increased rapidly in hypothyroidism after radioiodine treatment. Normalization of thyroid hormone levels due to l-thyroxine replacement did not alter the plasma ghrelin level significantly. When euthyroidism was achieved, plasma ghrelin levels correlated positively with the concentrations observed in hyperthyroidism and hypothyroidism, which may suggest individual parallel fluctuations of plasma ghrelin in the same patient. The relationship between thyroid function and ghrelin secretion has not been established yet. The presence of ghrelin and GHS-R has been demonstrated in the thyroid. However, the differences between their expression in parafollicular and follicular cells, as well as in benign and malignant thyroid diseases are still the subject of discussion [19,20,27,29,40,41,46]. Since ghrelin is expressed mainly in parafollicular cells and GHS-R was observed in follicular cells, it has been suggested that ghrelin may influence follicular cells in a paracrine manner [29]. Since then, various studies Table 1 Biochemical and clinical characteristics of the patients in hyperthyroid, hypothyroid and euthyroid states (normal ranges: TSH, 0.27–4.2 IU/ml; fT4 , 11.521 pmol/l; fT3 , 3.9–6.7 pmol/l) (* statistically significant difference in comparison to hyperthyroidism). Hyperthyroidism TSH (IU/ml) fT4 (pmol/l) fT3 (pmol/l) BMI (kg/m2 ) Ghrelin (pg/ml)
114
0.008 66.4 29 24.4 160.1
± ± ± ± ±
0.002 29.1 12.6 6 90.5
Hypothyroidism 35.3 5.7 3 25.9 364.6
± ± ± ± ±
19.6 3 1.8 6.1 269.4*
Euthyroidism 2.6 18.3 4.8 26.2 251.8
± ± ± ± ±
1.5 5.4 0.9 6.9 132.9*
Please cite this article in press as: Ruchala M, et al. Individual plasma ghrelin changes in the same patients in hyperthyroid, hypothyroid and euthyroid state. Peptides (2013), http://dx.doi.org/10.1016/j.peptides.2013.10.018
133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151
G Model PEP 69100 1–4
ARTICLE IN PRESS M. Ruchala et al. / Peptides xxx (2013) xxx–xxx
152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188
189
190 191 192 193 194 195 196
197
198 199 200 201
202
203 204 205 206 207 208 209 210 211
have analyzed the relationship between ghrelin release and thyroid function. Kluge et al. revealed that ghrelin induced a slight increase of fT4 levels and a considerable decrease of TSH levels in humans [21]. The authors concluded that TSH suppression might have been caused by either a negative feedback mechanism after fT4 rise, or by a ghrelininduced hypothalamic effect, or both. In rats ghrelin reduced TSH secretion and consequently inhibited thyroid hormone production [34]. On the other hand, Ciuoli et al. demonstrated that recombinant human TSH significantly decreased ghrelin concentration [6]. Furthermore, ghrelin was demonstrated to potentiate the proliferative effects of TSH on the growth of rat thyrocytes [26,28] and to increase TSH-induced expression of thyroglobulin, thyroperoxidase and the sodium/iodide symporter (NIS) [26]. Therefore, the relationship between ghrelin and thyroid function is highly probable. In contrast to hypothyroidism – where the thyroid hormone insufficiency disturbs the appropriate use of energy resources – hyperthyroidsim is a hypermetabolic state. In our opinion, plasma ghrelin fluctuations may reflect metabolic changes in thyroid disorders. In this study we observed a significant rise of the plasma ghrelin level during the transition from hyper- to hypothyroidism. We assume, that the increase in the plasma ghrelin level in hypothyroid patients may be understood as a response of the prometabolic peptide to improve metabolic processes. As mentioned before, plasma ghrelin changes may also result from other sources. It is important to highlight kidney dysfunction associated with thyroid disorders [25]. Changes in renal blood flow and glomerular filtration may obviously influence ghrelin elimination. Moreover, biologically active acylated ghrelin is bounded by lipoproteins [8]. Since both hypo- and hyperthyroidism may alter cholesterol fractions, plasma ghrelin changes may also result from dyslipoproteinemia. Finally, it has been also suggested that ghrelin concentration in thyroid disorders may be influenced by insulin level [13,30,39]. Insulin resistance and hyperinsulinemia associated with hyperthyroidism have been suggested to be factors decreasing ghrelin release.
5. Conclusions Our study revealed changes in individual plasma ghrelin concentrations in the same patients analyzed in three different thyreometabolic states. This observation suggests the involvement of ghrelin in the regulation of metabolic disturbances associated with hyper- and hypothyroidism. It cannot be excluded that in thyroid disorders ghrelin acts as a compensatory factor that helps to balance metabolic disturbances.
Acknowledgements The study was supported by a grant from the Polish Ministry of Science and Higher Education (NN 402 366638) and by a grant from the Poznan University of Medical Sciences (501-01-0222135506171).
References [1] Altinova AE, Törüner FB, Aktürk M, Elbe˘g S, Yetkin I, Cakir N, et al. Reduced serum acylated ghrelin levels in patients with hyperthyroidism. Horm Res 2006;65(6):295–9. [2] Altinova AE, Toruner F, Karakoc A, Yetkin I, Ayvaz G, Cakir N, et al. Serum ghrelin levels in patients with Hashimoto’s thyroiditis. Thyroid 2006;16(12):1259–64. [3] Ariyasu H, Takaya K, Tagami T, Ogawa Y, Hosoda K, Akamizu T, et al. Stomach is a major source of circulating ghrelin, and feeding state determines plasma ghrelin-like immunoreactivity levels in humans. J Clin Endocrinol Metab 2001;86:4753–8.
3
[4] Braclik M, Marcisz C, Giebel S, Orzeł A. Serum leptin and ghrelin levels in premenopausal women with stable body mass index during treatment of thyroid dysfunction. Thyroid 2008;18(5):545–50. [5] Cassoni P, Papotti M, Catapano F, Ghè C, Deghenghi R, Ghigo E, et al. Specific binding sites for synthetic growth hormone secretagogues in non-tumoral and neoplastic human thyroid tissue. J Endocrinol 2000;165:139–46. [6] Ciuoli C, Brusco L, Theodoropoulou A, Castagna MG, Neri O, Pasqui L, et al. Effects of acute recombinant human TSH on serum ghrelin levels. Front Endocrinol (Lausanne) 2011;2:94. [7] Cummings DE. Ghrelin and the short- and long-term regulation of appetite and body weight. Physiol Behav 2006;89(1):71–84. [8] De Vriese C, Hacquebard M, Gregoire F, Carpentier Y, Delporte C. Ghrelin interacts with human plasma lipoproteins. Endocrinology 2007;148(5):2355–62. [9] Delhanty PJ, Neggers SJ, van der Lely AJ. Mechanisms in endocrinology: Ghrelin: the differences between acyl- and des-acyl ghrelin. Eur J Endocrinol 2012;167(5):601–8. [10] El Gawad SS, El Kenawy F, Mousa AA, Omar AA. Plasma levels of resistin and ghrelin before and after treatment in patients with hyperthyroidism. Endocr Pract 2012;18(3):376–81 (abstract). [11] Fujimiya M, Ataka K, Asakawa A, Chen CY, Kato I, Inui A. Ghrelin, des-acyl ghrelin and obestatin on the gastrointestinal motility. Peptides 2011;32(11):2348–51. [12] Garcia JM, Garcia-Touza M, Hijazi RA, et al. Active ghrelin levels and active to total ghrelin ratio in cancer-induced cachexia. J Clin Endocrinol Metab 2005;90(5):2920–6. [13] Giménez-Palop O, Giménez-Pérez G, Mauricio D, Berlanga E, Potau N, Vilardell C, et al. Circulating ghrelin in thyroid dysfunction is related to insulin resistance and not to hunger, food intake or anthropometric changes. Eur J Endocrinol 2005;153(1):73–9. [14] Gjedde S, Vestergaard ET, Gormsen LC, Riis AL, Rungby J, Møller N, et al. Serum ghrelin levels are increased in hypothyroid patients and become normalized by l-thyroxine treatment. J Clin Endocrinol Metab 2008;93(6):2277–80. [15] Gnanapavan S, Kola B, Bustin SA, Morris DG, McGee P, Fairclough P, et al. The tissue distribution of the mRNA of ghrelin and subtypes of its receptor, GHS-R, in humans. J Clin Endocrinol Metab 2002;87:2988–91. [16] Gurgul E, Ruchala M, Kosowicz J, Zamyslowska H, Wrotkowska E, Moczko J, et al. Ghrelin and obestatin in thyroid dysfunction. Endokrynol Pol 2012;63(6):456–62. [17] Hosoda H, Kojima M, Mizushima T, Shimizu S, Kangawa K. Structural divergence of human ghrelin. Identification of multiple ghrelin-derived molecules produced by post-translational processing. J Biol Chem 2003;278:64–70. [18] Jeffery PL, Murray RE, Yeh AH, McNamara JF, Duncan RP, Francis GD, et al. Expression and function of the ghrelin axis, including a novel preproghrelin isoform, in human breast cancer tissues and cell lines. Endocr Relat Cancer 2005;12(4):839–50. [19] Kanamoto N, Akamizu T, Hosoda H, Hataya Y, Ariyasu H, Takaya K, et al. Substantial production of ghrelin by a human medullary thyroid carcinoma cell line. Clin Endocrinol Metab 2001;86(10):4984–90. [20] Karaoglu A, Aydin S, Dagli AF, Cummings DE, Ozercan IH, Canatan H, et al. Expression of obestatin and ghrelin in papillary thyroid carcinoma. Mol Cell Biochem 2009;323(1–2):113–8. [21] Kluge M, Riedl S, Uhr M, Schmidt D, Zhang X, Yassouridis A, et al. Ghrelin affects the hypothalamus-pituitary-thyroid (HPT) axis in humans by increasing free thyroxine (fT4 ) and decreasing TSH in plasma. Eur J Endocrinol 2010;162(6):1059–65. [22] Kojima M, Hosoda AH, Date Y, Nakazato M, Matsuo H, Kangawa K. Ghrelin is a growth hormone releasing acylated peptide from stomach. Nature 1999;402:656–60. [23] Kosowicz J, Baumann-Antczak A, Ruchala M, Gryczynska M, Gurgul E, Sowinski J. Thyroid hormones affect plasma ghrelin and obestatin levels. Horm Metab Res 2011;43(2):121–5. [24] Kosowicz J, Baumann-Antczak A, Zamyslowska H, Sowinski J. Technological difficulties in ghrelin and obestatin assays. Endokrynol Pol 2011;62(4):336–9. [25] Mariani LH, Berns JS. The renal manifestations of thyroid disease. J Am Soc Nephrol 2012;23(1):22–6. [26] Morillo-Bernal J, Fernández-Santos JM, De Miguel M, García-Marín R, GordilloMartínez F, Díaz-Parrado E, et al. Ghrelin potentiates TSH-induced expression of the thyroid tissue-specific genes thyroglobulin, thyroperoxidase and sodiumiodine symporter, in rat PC-Cl3 cells. Peptides 2011;32(11):2333–9. [27] Papotti M, Ghè C, Cassoni P, Catapano F, Deghenghi R, Ghigo E, et al. Growth hormone secretagogue binding sites in peripheral human tissues. J Clin Endocrinol Metab 2000;85(10):3803–7. [28] Park YJ, Lee YJ, Kim SH, Joung DS, Kim BJ, So I, et al. Ghrelin enhances the proliferating effect of thyroid stimulating hormone in FRTL-5 thyroid cells. Mol Cell Endocrinol 2008;285(1-2):19–25. [29] Raghay K, Garcia-Caballero T, Nogueiras R, Morel G, Beiras A, Dieguez C, et al. Ghrelin localization in rat and human thyroid and parathyroid glands and tumors. Histochem Cell Biol 2006;89:400–9. [30] Riis AL, Hansen TK, Møller N, Weeke J, Jørgensen JO. Hyperthyroidism is associated with suppressed circulating ghrelin levels. J Clin Endocrinol Metab 2003;88(2):853–7. Erratum in: J Clin Endocrinol Metab 2003; 88(5):2112. [31] Röjdmark S, Calissendorff J, Danielsson O, Brismar K. Hunger-satiety signals in patients with Graves’ thyrotoxicosis before, during, and after long-term pharmacological treatment. Endocrine 2005;27(1):55–61. [32] Ruchala M, Rafinska L, Kosowicz J, Gurgul E, Sawinski P, Biczysko M, et al. The analysis of exogenous ghrelin plasma activity and tissue distribution. Neuro Endocrinol Lett 2012;33(2):191–5.
Please cite this article in press as: Ruchala M, et al. Individual plasma ghrelin changes in the same patients in hyperthyroid, hypothyroid and euthyroid state. Peptides (2013), http://dx.doi.org/10.1016/j.peptides.2013.10.018
212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297
G Model PEP 69100 1–4 4
298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316
ARTICLE IN PRESS M. Ruchala et al. / Peptides xxx (2013) xxx–xxx
[33] Sadegholvad A, Afkhamizadeh M, Ranjbar-Omrani G. Serum ghrelin changes in thyroid dysfunction. Arch Iran Med 2007;10(2):168–70. ´ c´ B, Stevanovic´ D, Milosevic´ V, Sekulic´ M, Starcevic´ V. Central [34] Sosic-Jurjevi ghrelin affects pituitary-thyroid axis: histomorphological and hormonal study in rats. Neuroendocrinology 2009;89(3):327–36. [35] Tack J, Depoortere I, Bisschops R, Verbeke K, Janssens J, Peeters T. Influence of ghrelin on gastric emptying and meal-related symptoms in idiopathic gastroparesis. Aliment Pharmacol Ther 2005;22(9):847–53. [36] Takaya K, Ariyasu H, Kanamoto N, Iwakura H, Yoshimoto A, Harada M, et al. Ghrelin strongly stimulates growth hormone release in humans. J Clin Endocrinol Metab 2000;85:4908–11. [37] Tanaka M, Naruo T, Yasuhara D, et al. Fasting plasma ghrelin levels in subtypes of anorexia nervosa. Psychoneuroendocrinology 2003;28:829–35. [38] Tanda ML, Lombardi V, Genovesi M, Ultimieri F, Lai A, Gandolfo M, et al. Plasma total and acylated ghrelin concentrations in patients with clinical and subclinical thyroid dysfunction. J Endocrinol Invest 2009;32(1):74–8. [39] Theodoropoulou A, Psyrogiannis A, Metallinos IC, Habeos I, Vgenakis AG, Kyriazopoulou V. Ghrelin response to oral glucose load in hyperthyroidism, before and after treatment with antithyroid drugs. J Endocrinol Invest 2009;32(2):94–7.
[40] Ueberberg B, Unger N, Saeger W, Mann K, Petersenn S. Expression of ghrelin and its receptor in human tissues. Horm Metab Res 2009;41(11): 814–21. [41] Volante M, Allia E, Fulcheri E, Cassoni P, Ghigo E, Muccioli G, et al. Ghrelin in fetal thyroid and follicular tumors and cell lines: expression and effects on tumor growth. Am J Pathol 2003;162:645–54. [42] Williams DL, Cummings DE. Regulation of ghrelin in physiologic and pathophysiologic states. J Nutr 2005;135:1320–5. [43] Wren AM, Seal LJ, Cohen MA, Brynes AE, Frost GS, Murphy KG, et al. Ghrelin enhances appetite and increases food intake in humans. J Clin Endocrinol Metab 2001;86(12):5992. [44] Yasuda T, Masaki T, Kakuma T, Yoshimatsu H. Centrally administered ghrelin suppresses sympathetic nerve activity in brown adipose tissue of rats. Neurosci Lett 2003;349(2):75–8. [45] Yoshimoto A, Mori K, Sugawara A, Mukoyama M, Yahata K, Suganami T, et al. Plasma ghrelin and desacyl ghrelin concentrations in renal failure. J Am Soc Nephrol 2002;13(11):2748–52. [46] Zhang YF, Wang HN, Hong TP. Ghrelin expression in the tissues of different thyroid diseases. Beijing Da Xue Xue Bao 2006;38:193–6 (abstract).
Please cite this article in press as: Ruchala M, et al. Individual plasma ghrelin changes in the same patients in hyperthyroid, hypothyroid and euthyroid state. Peptides (2013), http://dx.doi.org/10.1016/j.peptides.2013.10.018
317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336
G Model PEP 69100 1–4
Peptides xxx (2013) xxx–xxx
Contents lists available at ScienceDirect
Peptides journal homepage: www.elsevier.com/locate/peptides
Individual plasma ghrelin changes in the same patients in hyperthyroid, hypothyroid and euthyroid state
1
2
3 4 5 6
Q1
Marek Ruchala a,1 , Edyta Gurgul a,∗,1 , Adam Stangierski a , Elzbieta Wrotkowska a , Jerzy Moczko b,2 a b
Department of Endocrinology, Metabolism and Internal Medicine, Poznan Medical University, 49 Przybyszewskiego St., 60-355 Poznan, Poland Department of Computer Science and Statistics, Poznan Medical University, 79 Dabrowskiego St., 60-529 Poznan, Poland
7
8
a r t i c l e
i n f o
a b s t r a c t
9 10 11 12 13
Article history: Received 2 September 2013 Received in revised form 21 October 2013 Accepted 21 October 2013 Available online xxx
14
20
Keywords: Ghrelin Hyperthyroidism Hypothyroidism Thyroid dysfunction Metabolism
21
1. Introduction
15 16 17 18 19
22 23 24 25 26 27 28 29 30 31 32 33 34
Ghrelin is a multifunctional peptide of widespread expression. Since it has been shown to influence energy homeostatis, its potential role in thyroid dysfunction may have clinical significance. In this study, plasma ghrelin changes have been analyzed in the same patients in three different thyroid states for the first time. The study group consisted of 16 patients who had been diagnosed with hyperthyroidism, were treated with radioiodine, developed hypothyroidism after treatment, and finally became euthyroid on lthyroxine substitution. In the initial state of hyperthyroidism plasma ghrelin levels correlated negatively with fT3 and fT4 . In hypothyroidism ghrelin concentration increased significantly (p < 0.05). Although the mean value of plasma ghrelin tended to decrease in the euthyroid state, the individual difference between hypothyroidism and euthyroidism was not significant. Plasma ghrelin in euthyroidism was still significantly higher than in hyperthyroidism (p < 0.05), and correlated positively with ghrelin levels in hyperthyroidism and hypothyroidism. In our opinion, plasma ghrelin fluctuations may reflect metabolic changes in patients with thyroid dysfunction. Moreover, it cannot be excluded that in thyroid disorders ghrelin acts as a compensatory factor, helping to balance metabolic disturbances. © 2013 Elsevier Inc. All rights reserved.
Ghrelin is a multifunctional peptide that was discovered in 1999 as the first natural ligand for the growth hormone – secretagogue receptor (GHS-R) [22]. GHS-R has two subtypes: GHS-R1a – a functional ghrelin receptor and GHS-R1b, whose role still needs to be analyzed [15,18]. A unique modification (n-octanoylation at Ser 3) enables acylated ghrelin to bind GHS-R1a and exert biological activity [17,22]. Des-acyl ghrelin was previously considered to be inactive, but recent studies have demonstrated that it may also have a biological function [9,11]. Ghrelin is produced mainly in neuroendocrine cells (X/A cells) of the gastric mucosa [3]. However, to a lesser extent, it is also secreted in the intestine, hypothalamus, pituitary and many other tissues [15,40].
Abbreviations: BMI, body mass index; EDTA, ethylenediaminetetraacetic acid; fT3 , free triiodothyronine; fT4 , free thyroxine; GHS-R, growth hormone – secretagogue receptor; NIS, sodium/iodide symporter; RIA, radioimmunoassay; TSH, thyrotropin. ∗ Corresponding author. Tel.: +48 618691330; fax: +48 618691682. E-mail address: [email protected] (E. Gurgul). 1 These authors contributed equally to this work. 2 Tel.: +48 61 854 68 08; fax: +48 61 854 68 08.
Ghrelin was initially described as the first endogenous growth hormone secretagogue, and proved to be a strong stimulator of growth hormone release [36]. Furthermore, it has been described as an essential regulator of metabolic processes, as it increases food intake, acts as an adipogenic factor, stimulates gastric emptying and reduces energy expenditure [35,43,44]. As a result, ghrelin causes energy saving effects, positive energy balance and weight gain [21]. Ghrelin secretion is regulated mainly by the metabolic state. Its plasma concentration is high during fasting and decreases in response to food intake [7]. Similarly, long-term negative energy balance states (anorexia, cachexia) increase ghrelin production while obesity, on the other hand, decreases ghrelin secretion [12,37,42]. It is well known that thyroid hormones play an important role in energy homeostasis. They increase the metabolic rate, thermogenesis and energy expenditure. Thus, hyperthyroidism as a hypermetabolic state is associated with increased appetite, but also with increased energy expenditure and weight loss. In contrast, hypothyroid patients present a decreased metabolic rate and weight gain. The presence of ghrelin receptors has been demonstrated in the thyroid [5,15,27,40]. Furthermore, exogenous ghrelin uptake in thyroid tissue has been shown to be notably high in rats [32]. Previous studies have revealed that in hyperthyroidism plasma ghrelin levels are decreased [1,4,10,13,16,23,30,31,38,39] and rise
0196-9781/$ – see front matter © 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.peptides.2013.10.018
Please cite this article in press as: Ruchala M, et al. Individual plasma ghrelin changes in the same patients in hyperthyroid, hypothyroid and euthyroid state. Peptides (2013), http://dx.doi.org/10.1016/j.peptides.2013.10.018
35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59
G Model PEP 69100 1–4
ARTICLE IN PRESS M. Ruchala et al. / Peptides xxx (2013) xxx–xxx
2
80
after treatment [10,13,30,31,38,39]. These observations were surprising in view of such symptoms as increased appetite and weight loss in hyperthyroid patients. Hypothyroidism has been predominantly associated with a high ghrelin level [4,14,23] that decreases after treatment [14]. Some authors did not notice any difference [13,33,38], or observed low plasma ghrelin levels in hypothyroid patients [2]. To the best of our knowledge, none of the previous studies evaluated plasma ghrelin concentrations in three different thyroid functional states in the same patients. Various individual factors influence plasma ghrelin levels, i.e. metabolic rate, kidney function, or lipoprotein concentration [8,42,45]. Thus, it seems that a comparison of three different groups of hyper-, hypo- and euthyroid patients may not always be accurately objective. Consequently, the aim of the study was to evaluate the fluctuations of plasma ghrelin concentrations in the same patients during their hyperthyroid, hypothyroid and euthyroid state. We assume that such an analysis may help to understand the dynamic changes of ghrelin concentration based only on the thyroid state at a given time, without the interference of other individual features.
81
2. Materials and methods
82
2.1. Study group
60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79
91
The study group consisted of 16 patients who had been diagnosed with hyperthyroidism (13 women and 3 men), were treated with radioiodine, developed hypothyroidism after treatment, and finally became euthyroid on l-thyroxine substitution. Plasma ghrelin concentration was assessed in these patients during the hyperthyroid, hypothyroid and euthyroid state. Blood samples were collected after a 10-h overnight fast and placed in polyethylene tubes containing plasma enzymes inhibitors (aprotinin and ethylenediaminetetraacetic acid – EDTA).
92
2.2. Laboratory methods
83 84 85 86 87 88 89 90
93 94 95 96 97 98 99 100
101
Total plasma ghrelin levels were measured in duplicate with a commercially available radioimmunoassay (RIA) (Phoenix Pharmaceuticals Inc.). Radioactivity of the samples was assessed in an automatic LKB-Wallace gamma counter. The technique of plasma ghrelin measurement has been already described [24]. Free thyroxine (fT4 ), free triiodothyronine (fT3 ) and thyrotropin (TSH) levels were assessed using an electrochemiluminescence method. 2.3. Statistical methods
105
Plasma ghrelin changes in the hyperthyroid, hypothyroid and euthyroid state were analyzed using the non-parametric Friedman test, and the post hoc multiple comparison tests. Correlations were assessed with the use of Spearman’s rank correlation coefficient.
106
2.4. Ethics
102 103 104
108
The study was conducted with the permission of Poznan University of Medical Sciences Ethical Committee.
109
3. Results
107
110 111 112 113
In the initial state of hyperthyroidism plasma ghrelin level (ghrelin 1) (160.1 ± 90.5 pg/ml) correlated negatively with fT3 (r = −0.67, p < 0.05) and fT4 (r = −0.83, p < 0.05). In hypothyroidism (ghrelin 2) (364.6 ± 269.4 pg/ml) it increased considerably (p < 0.05)
Fig. 1. Individual plasma ghrelin changes in each patient. Plasma ghrelin levels evaluated in hyperthyroidism, hypothyroidism and euthyroidism.
(Fig. 1). Although the mean value of plasma ghrelin concentration tended to decrease when the patients achieved euthyroidism, the individual difference between hypothyroidism (ghrelin 2) and euthyroidism (ghrelin 3) (251.8 ± 132.9 pg/ml) was not significant. Plasma ghrelin in euthyroidism was still significantly higher than in the initial state of hyperthyroidism (p < 0.05) and correlated positively with plasma ghrelin concentrations measured in hyperthyroidism (r = 0.65, p < 0.05) and hypothyroidism (r = 0.93, p < 0.05). At the moment of submitting this manuscript two patients were still characterized by increased TSH levels (5.9 IU/ml and 5.1 IU/ml). However, they presented a major clinical improvement and notable decrease of TSH concentrations in comparison to the hypothyroid state (hypothyroid TSH 59.9 IU/ml and 50.81 IU/ml, respectively). One patient was evaluated during hyperthyroidism, then in euthyroidism after radioiodine treatment, and finally in hypothyroidism that developed afterwards (Table 1). 4. Discussion
115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131
132
In our study, in the initial state of hyperthyroidism plasma ghrelin levels correlated negatively with free thyroid hormones (fT3 and fT4 ). Hyperthyroid patients presented a low ghrelin level, which increased rapidly in hypothyroidism after radioiodine treatment. Normalization of thyroid hormone levels due to l-thyroxine replacement did not alter the plasma ghrelin level significantly. When euthyroidism was achieved, plasma ghrelin levels correlated positively with the concentrations observed in hyperthyroidism and hypothyroidism, which may suggest individual parallel fluctuations of plasma ghrelin in the same patient. The relationship between thyroid function and ghrelin secretion has not been established yet. The presence of ghrelin and GHS-R has been demonstrated in the thyroid. However, the differences between their expression in parafollicular and follicular cells, as well as in benign and malignant thyroid diseases are still the subject of discussion [19,20,27,29,40,41,46]. Since ghrelin is expressed mainly in parafollicular cells and GHS-R was observed in follicular cells, it has been suggested that ghrelin may influence follicular cells in a paracrine manner [29]. Since then, various studies Table 1 Biochemical and clinical characteristics of the patients in hyperthyroid, hypothyroid and euthyroid states (normal ranges: TSH, 0.27–4.2 IU/ml; fT4 , 11.521 pmol/l; fT3 , 3.9–6.7 pmol/l) (* statistically significant difference in comparison to hyperthyroidism). Hyperthyroidism TSH (IU/ml) fT4 (pmol/l) fT3 (pmol/l) BMI (kg/m2 ) Ghrelin (pg/ml)
114
0.008 66.4 29 24.4 160.1
± ± ± ± ±
0.002 29.1 12.6 6 90.5
Hypothyroidism 35.3 5.7 3 25.9 364.6
± ± ± ± ±
19.6 3 1.8 6.1 269.4*
Euthyroidism 2.6 18.3 4.8 26.2 251.8
± ± ± ± ±
1.5 5.4 0.9 6.9 132.9*
Please cite this article in press as: Ruchala M, et al. Individual plasma ghrelin changes in the same patients in hyperthyroid, hypothyroid and euthyroid state. Peptides (2013), http://dx.doi.org/10.1016/j.peptides.2013.10.018
133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151
G Model PEP 69100 1–4
ARTICLE IN PRESS M. Ruchala et al. / Peptides xxx (2013) xxx–xxx
152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188
189
190 191 192 193 194 195 196
197
198 199 200 201
202
203 204 205 206 207 208 209 210 211
have analyzed the relationship between ghrelin release and thyroid function. Kluge et al. revealed that ghrelin induced a slight increase of fT4 levels and a considerable decrease of TSH levels in humans [21]. The authors concluded that TSH suppression might have been caused by either a negative feedback mechanism after fT4 rise, or by a ghrelininduced hypothalamic effect, or both. In rats ghrelin reduced TSH secretion and consequently inhibited thyroid hormone production [34]. On the other hand, Ciuoli et al. demonstrated that recombinant human TSH significantly decreased ghrelin concentration [6]. Furthermore, ghrelin was demonstrated to potentiate the proliferative effects of TSH on the growth of rat thyrocytes [26,28] and to increase TSH-induced expression of thyroglobulin, thyroperoxidase and the sodium/iodide symporter (NIS) [26]. Therefore, the relationship between ghrelin and thyroid function is highly probable. In contrast to hypothyroidism – where the thyroid hormone insufficiency disturbs the appropriate use of energy resources – hyperthyroidsim is a hypermetabolic state. In our opinion, plasma ghrelin fluctuations may reflect metabolic changes in thyroid disorders. In this study we observed a significant rise of the plasma ghrelin level during the transition from hyper- to hypothyroidism. We assume, that the increase in the plasma ghrelin level in hypothyroid patients may be understood as a response of the prometabolic peptide to improve metabolic processes. As mentioned before, plasma ghrelin changes may also result from other sources. It is important to highlight kidney dysfunction associated with thyroid disorders [25]. Changes in renal blood flow and glomerular filtration may obviously influence ghrelin elimination. Moreover, biologically active acylated ghrelin is bounded by lipoproteins [8]. Since both hypo- and hyperthyroidism may alter cholesterol fractions, plasma ghrelin changes may also result from dyslipoproteinemia. Finally, it has been also suggested that ghrelin concentration in thyroid disorders may be influenced by insulin level [13,30,39]. Insulin resistance and hyperinsulinemia associated with hyperthyroidism have been suggested to be factors decreasing ghrelin release.
5. Conclusions Our study revealed changes in individual plasma ghrelin concentrations in the same patients analyzed in three different thyreometabolic states. This observation suggests the involvement of ghrelin in the regulation of metabolic disturbances associated with hyper- and hypothyroidism. It cannot be excluded that in thyroid disorders ghrelin acts as a compensatory factor that helps to balance metabolic disturbances.
Acknowledgements The study was supported by a grant from the Polish Ministry of Science and Higher Education (NN 402 366638) and by a grant from the Poznan University of Medical Sciences (501-01-0222135506171).
References [1] Altinova AE, Törüner FB, Aktürk M, Elbe˘g S, Yetkin I, Cakir N, et al. Reduced serum acylated ghrelin levels in patients with hyperthyroidism. Horm Res 2006;65(6):295–9. [2] Altinova AE, Toruner F, Karakoc A, Yetkin I, Ayvaz G, Cakir N, et al. Serum ghrelin levels in patients with Hashimoto’s thyroiditis. Thyroid 2006;16(12):1259–64. [3] Ariyasu H, Takaya K, Tagami T, Ogawa Y, Hosoda K, Akamizu T, et al. Stomach is a major source of circulating ghrelin, and feeding state determines plasma ghrelin-like immunoreactivity levels in humans. J Clin Endocrinol Metab 2001;86:4753–8.
3
[4] Braclik M, Marcisz C, Giebel S, Orzeł A. Serum leptin and ghrelin levels in premenopausal women with stable body mass index during treatment of thyroid dysfunction. Thyroid 2008;18(5):545–50. [5] Cassoni P, Papotti M, Catapano F, Ghè C, Deghenghi R, Ghigo E, et al. Specific binding sites for synthetic growth hormone secretagogues in non-tumoral and neoplastic human thyroid tissue. J Endocrinol 2000;165:139–46. [6] Ciuoli C, Brusco L, Theodoropoulou A, Castagna MG, Neri O, Pasqui L, et al. Effects of acute recombinant human TSH on serum ghrelin levels. Front Endocrinol (Lausanne) 2011;2:94. [7] Cummings DE. Ghrelin and the short- and long-term regulation of appetite and body weight. Physiol Behav 2006;89(1):71–84. [8] De Vriese C, Hacquebard M, Gregoire F, Carpentier Y, Delporte C. Ghrelin interacts with human plasma lipoproteins. Endocrinology 2007;148(5):2355–62. [9] Delhanty PJ, Neggers SJ, van der Lely AJ. Mechanisms in endocrinology: Ghrelin: the differences between acyl- and des-acyl ghrelin. Eur J Endocrinol 2012;167(5):601–8. [10] El Gawad SS, El Kenawy F, Mousa AA, Omar AA. Plasma levels of resistin and ghrelin before and after treatment in patients with hyperthyroidism. Endocr Pract 2012;18(3):376–81 (abstract). [11] Fujimiya M, Ataka K, Asakawa A, Chen CY, Kato I, Inui A. Ghrelin, des-acyl ghrelin and obestatin on the gastrointestinal motility. Peptides 2011;32(11):2348–51. [12] Garcia JM, Garcia-Touza M, Hijazi RA, et al. Active ghrelin levels and active to total ghrelin ratio in cancer-induced cachexia. J Clin Endocrinol Metab 2005;90(5):2920–6. [13] Giménez-Palop O, Giménez-Pérez G, Mauricio D, Berlanga E, Potau N, Vilardell C, et al. Circulating ghrelin in thyroid dysfunction is related to insulin resistance and not to hunger, food intake or anthropometric changes. Eur J Endocrinol 2005;153(1):73–9. [14] Gjedde S, Vestergaard ET, Gormsen LC, Riis AL, Rungby J, Møller N, et al. Serum ghrelin levels are increased in hypothyroid patients and become normalized by l-thyroxine treatment. J Clin Endocrinol Metab 2008;93(6):2277–80. [15] Gnanapavan S, Kola B, Bustin SA, Morris DG, McGee P, Fairclough P, et al. The tissue distribution of the mRNA of ghrelin and subtypes of its receptor, GHS-R, in humans. J Clin Endocrinol Metab 2002;87:2988–91. [16] Gurgul E, Ruchala M, Kosowicz J, Zamyslowska H, Wrotkowska E, Moczko J, et al. Ghrelin and obestatin in thyroid dysfunction. Endokrynol Pol 2012;63(6):456–62. [17] Hosoda H, Kojima M, Mizushima T, Shimizu S, Kangawa K. Structural divergence of human ghrelin. Identification of multiple ghrelin-derived molecules produced by post-translational processing. J Biol Chem 2003;278:64–70. [18] Jeffery PL, Murray RE, Yeh AH, McNamara JF, Duncan RP, Francis GD, et al. Expression and function of the ghrelin axis, including a novel preproghrelin isoform, in human breast cancer tissues and cell lines. Endocr Relat Cancer 2005;12(4):839–50. [19] Kanamoto N, Akamizu T, Hosoda H, Hataya Y, Ariyasu H, Takaya K, et al. Substantial production of ghrelin by a human medullary thyroid carcinoma cell line. Clin Endocrinol Metab 2001;86(10):4984–90. [20] Karaoglu A, Aydin S, Dagli AF, Cummings DE, Ozercan IH, Canatan H, et al. Expression of obestatin and ghrelin in papillary thyroid carcinoma. Mol Cell Biochem 2009;323(1–2):113–8. [21] Kluge M, Riedl S, Uhr M, Schmidt D, Zhang X, Yassouridis A, et al. Ghrelin affects the hypothalamus-pituitary-thyroid (HPT) axis in humans by increasing free thyroxine (fT4 ) and decreasing TSH in plasma. Eur J Endocrinol 2010;162(6):1059–65. [22] Kojima M, Hosoda AH, Date Y, Nakazato M, Matsuo H, Kangawa K. Ghrelin is a growth hormone releasing acylated peptide from stomach. Nature 1999;402:656–60. [23] Kosowicz J, Baumann-Antczak A, Ruchala M, Gryczynska M, Gurgul E, Sowinski J. Thyroid hormones affect plasma ghrelin and obestatin levels. Horm Metab Res 2011;43(2):121–5. [24] Kosowicz J, Baumann-Antczak A, Zamyslowska H, Sowinski J. Technological difficulties in ghrelin and obestatin assays. Endokrynol Pol 2011;62(4):336–9. [25] Mariani LH, Berns JS. The renal manifestations of thyroid disease. J Am Soc Nephrol 2012;23(1):22–6. [26] Morillo-Bernal J, Fernández-Santos JM, De Miguel M, García-Marín R, GordilloMartínez F, Díaz-Parrado E, et al. Ghrelin potentiates TSH-induced expression of the thyroid tissue-specific genes thyroglobulin, thyroperoxidase and sodiumiodine symporter, in rat PC-Cl3 cells. Peptides 2011;32(11):2333–9. [27] Papotti M, Ghè C, Cassoni P, Catapano F, Deghenghi R, Ghigo E, et al. Growth hormone secretagogue binding sites in peripheral human tissues. J Clin Endocrinol Metab 2000;85(10):3803–7. [28] Park YJ, Lee YJ, Kim SH, Joung DS, Kim BJ, So I, et al. Ghrelin enhances the proliferating effect of thyroid stimulating hormone in FRTL-5 thyroid cells. Mol Cell Endocrinol 2008;285(1-2):19–25. [29] Raghay K, Garcia-Caballero T, Nogueiras R, Morel G, Beiras A, Dieguez C, et al. Ghrelin localization in rat and human thyroid and parathyroid glands and tumors. Histochem Cell Biol 2006;89:400–9. [30] Riis AL, Hansen TK, Møller N, Weeke J, Jørgensen JO. Hyperthyroidism is associated with suppressed circulating ghrelin levels. J Clin Endocrinol Metab 2003;88(2):853–7. Erratum in: J Clin Endocrinol Metab 2003; 88(5):2112. [31] Röjdmark S, Calissendorff J, Danielsson O, Brismar K. Hunger-satiety signals in patients with Graves’ thyrotoxicosis before, during, and after long-term pharmacological treatment. Endocrine 2005;27(1):55–61. [32] Ruchala M, Rafinska L, Kosowicz J, Gurgul E, Sawinski P, Biczysko M, et al. The analysis of exogenous ghrelin plasma activity and tissue distribution. Neuro Endocrinol Lett 2012;33(2):191–5.
Please cite this article in press as: Ruchala M, et al. Individual plasma ghrelin changes in the same patients in hyperthyroid, hypothyroid and euthyroid state. Peptides (2013), http://dx.doi.org/10.1016/j.peptides.2013.10.018
212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297
G Model PEP 69100 1–4 4
298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316
ARTICLE IN PRESS M. Ruchala et al. / Peptides xxx (2013) xxx–xxx
[33] Sadegholvad A, Afkhamizadeh M, Ranjbar-Omrani G. Serum ghrelin changes in thyroid dysfunction. Arch Iran Med 2007;10(2):168–70. ´ c´ B, Stevanovic´ D, Milosevic´ V, Sekulic´ M, Starcevic´ V. Central [34] Sosic-Jurjevi ghrelin affects pituitary-thyroid axis: histomorphological and hormonal study in rats. Neuroendocrinology 2009;89(3):327–36. [35] Tack J, Depoortere I, Bisschops R, Verbeke K, Janssens J, Peeters T. Influence of ghrelin on gastric emptying and meal-related symptoms in idiopathic gastroparesis. Aliment Pharmacol Ther 2005;22(9):847–53. [36] Takaya K, Ariyasu H, Kanamoto N, Iwakura H, Yoshimoto A, Harada M, et al. Ghrelin strongly stimulates growth hormone release in humans. J Clin Endocrinol Metab 2000;85:4908–11. [37] Tanaka M, Naruo T, Yasuhara D, et al. Fasting plasma ghrelin levels in subtypes of anorexia nervosa. Psychoneuroendocrinology 2003;28:829–35. [38] Tanda ML, Lombardi V, Genovesi M, Ultimieri F, Lai A, Gandolfo M, et al. Plasma total and acylated ghrelin concentrations in patients with clinical and subclinical thyroid dysfunction. J Endocrinol Invest 2009;32(1):74–8. [39] Theodoropoulou A, Psyrogiannis A, Metallinos IC, Habeos I, Vgenakis AG, Kyriazopoulou V. Ghrelin response to oral glucose load in hyperthyroidism, before and after treatment with antithyroid drugs. J Endocrinol Invest 2009;32(2):94–7.
[40] Ueberberg B, Unger N, Saeger W, Mann K, Petersenn S. Expression of ghrelin and its receptor in human tissues. Horm Metab Res 2009;41(11): 814–21. [41] Volante M, Allia E, Fulcheri E, Cassoni P, Ghigo E, Muccioli G, et al. Ghrelin in fetal thyroid and follicular tumors and cell lines: expression and effects on tumor growth. Am J Pathol 2003;162:645–54. [42] Williams DL, Cummings DE. Regulation of ghrelin in physiologic and pathophysiologic states. J Nutr 2005;135:1320–5. [43] Wren AM, Seal LJ, Cohen MA, Brynes AE, Frost GS, Murphy KG, et al. Ghrelin enhances appetite and increases food intake in humans. J Clin Endocrinol Metab 2001;86(12):5992. [44] Yasuda T, Masaki T, Kakuma T, Yoshimatsu H. Centrally administered ghrelin suppresses sympathetic nerve activity in brown adipose tissue of rats. Neurosci Lett 2003;349(2):75–8. [45] Yoshimoto A, Mori K, Sugawara A, Mukoyama M, Yahata K, Suganami T, et al. Plasma ghrelin and desacyl ghrelin concentrations in renal failure. J Am Soc Nephrol 2002;13(11):2748–52. [46] Zhang YF, Wang HN, Hong TP. Ghrelin expression in the tissues of different thyroid diseases. Beijing Da Xue Xue Bao 2006;38:193–6 (abstract).
Please cite this article in press as: Ruchala M, et al. Individual plasma ghrelin changes in the same patients in hyperthyroid, hypothyroid and euthyroid state. Peptides (2013), http://dx.doi.org/10.1016/j.peptides.2013.10.018
317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336