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Abnormal responsiveness of growth hormone to human corticotropin-releasing hormone in major depressive disorder
Journal
of Affective
Disorders,
245
14 (1988) 245-250
Elsevier
JAD 00534
Abnormal responsiveness of growth hormone to human corticotropin-releasing hormone in major depressive disorder Klaus-Peter ’
Department
of Psychiatry, F.R.G.
and
Lesch’, Gerd Lauxl, Heinrich M. Schulte2, Hans Pfi.iller3 and Helmut Beckmann’
University of Wiirzburg, 8700
3 Department
of Endocrinology,
Wiirzburg, F. R.G., Pediatric
’ Department
of Medicine
Clinic, University of Wiirzburg,
8700
I, University of Kiel, 2300 Kiel, Wiirzburg,
F.R.G.
(Received 8 June 1987) (Revision received 16 November 1987) (Accepted 18 November 1987)
Summary Plasma growth hormone (GH) release after injection of 100 pg synthetic human corticotropin-releasing hormone (hCRH) was investigated in 11 patients with major depressive disorder and normal controls matched for gender, age, body weight and ovarian status. In contrast to controls, who exhibited no significant GH response to CRH, depressed patients showed a significant net increase in GH secretion following CRH administration. The abnormal GH response to CRH was not correlated with baseline corticotropin (ACTH) and cortisol nor with CRH-induced ACTH and cortisol response. The implications of these findings are discussed with reference to such factors as a-adrenergic hyperactivity, hypothalamicpituitary system dysregulation, drug interference, non-specific stress responses and abnormal neuroendocrine circadian rhythms in major depression.
Key words: Corticotropin-releasing
hormone; Growth hormone; Depression
A variety of neuroendocrine derangements have been described in association with major depression. These include failure to suppress cortisol after dexamethasone (Carroll et al., 1982) blunting of thyrotropin (TSH) response to thyrotropin-
Address for correspondence: Dr. K.-P. Lesch, Department of Psychiatry, University of Wiirzburg, Fkhsleinstrasse 15, 8700 Wiirzburg, F.R.G. 0165-0327/88/$03.50
0 1988 Elsevier Science Publishers
releasing hormone (TRH) (Loosen and Prange, 1982), attenuation of corticotropin (ACTH) after corticotropin-releasing hormone (CRH) stimulation (Gold et al., 1984; Holsboer et al., 1984; Lesch et al., 1987) and deficient growth hormone (GH) response to the a,-adrenoceptor agonist clonidine (Matussek et al., 1980). A more controversial finding is a ‘paradoxical’ GH response to TRH (Linkowski et al., 1980). However, more recent studies indicate that some depressives also show anomalous GH elevations after CRH (Gold et al., 1984).
B.V. (Biomedical
Division)
246
CRH, a 41-amino acid peptide isolated from the hypothalamus, is the primary neuroregulator of the secretion of pro-opiomelanocortin (POMC)derived peptides from the anterior pituitary (Vale et al., 1981). Although ‘paradoxical’ GH responses were reported in chair-restrained primates (Schulte et al., 1982) and in patients with acromegaly (Pieters et al., 1984) plasma GH levels were not influenced by the administration of CRH to healthy adults (Chrousos et al., 1983). The mechanisms underlying abnormal GH responses to CRH in depressed patients have not been clarified and a number of theoretical and methodological questions remain as to the nature and interpretation of ‘paradoxical’ GH output after CRH in major depression. The present investigation aimed to reassess patterns of plasma GH secretion after CRH in patients with major depressive disorder (both unipolar and bipolar) matched for gender, age, body weight and ovarian status with normal controls. Methods
TABLE
DATA
(MEAN + SEM)
Depressed (n=ll)
patients
Normal controls (12’11)
Age (years)
40.5 +4.6
(20-63)
Body weight (kg)
6X.X i 3.5
(52-8X)
Female Male
6 5
40.5 i 4.5 ( 19-64) 69.2 i 3.0 (52-90) 6 5
Age of onset of 1st depressive episode (years) Number of brevious affective episodes Duration of present depressive episode (months) Total duration of illness (years) Hamilton Depression SWVZ Time medication-free (days)
Subjects Eleven patients, six women and five men, fulfilled the requirements for major depressive disorder, endogenous subtype according to the Research Diagnostic Criteria (RDC) (Spitzer et al., 1978). The patients were diagnosed by two psychiatrists on the basis of a clinical interview using DSM-III (American Psychiatric Association, 1980) criteria. Seven patients were diagnosed as having a major depressive episode (MDE, without melancholia), the remaining four patients as having MDE with melancholia. Within the overall group of patients, seven were unipolar and four were bipolar patients. All investigations were performed after admission to the Department of Psychiatry, University of Wtirzburg. After given written informed consent, all patients were evaluated by physical examination and routine laboratory screening to exclude major physical disorder. Their ages were between 20 and 63 years (mean &- SEM = 40.5 _t 4.6 years), their body weights were 68.8 f 3.5 kg. of the six female patients five were post-menopausal. The study was performed after an average drug-free period of 9 days. In six patients the drug-free period exceeded 14 days;
1
DEMOGRAPHIC AND CLINICAL IN PATIENTS AND CONTROLS
35X24.4
(17-53)
3.0i0.42
(lm 6)
2.5kO.4
(l& 5)
4.7i1.4
(1-12)
25.5 f 1.1 (20-33) 9.051.7
(3-14)
< 5 -
five patients received amitriptyline, chlorimipra. mine, doxepine or mianserin prior to a drug-free period of 3 days. The 21-item Hamilton Rating Scale for Depression (HRSD) (Hamilton, 1960) was completed for each patient 1 day prior to the CRH test. Mean depression scale score was 25.5 f 1.1. Eleven normal controls (Table 1) were quadruple-matched for gender (five male, six female), age (40.5 + 4.5 years), weight (69.2 f 3.0 kg) and ovarian status (three pre-menopausal, three postmenopausal) and participated on a paid voluntary basis after written informed consent had been obtained. They reported no history of psychiatric disorders in first-degree relatives and none had taken any medication for at least 4 weeks before admission for study. They had refrained from alcohol use, were not sleep-deprived and were not involved in current stressful life events. Procedure The CRH stimulation tests were conducted on all subjects at rest in bed after a 6-h fast at 6:00
247
p.m. One hour after the insertion of an intravenous line in an antecubital vein, 100 pg synthetic human CRH (Bissendorf, Wedemark, F.R.G.), dissolved in 1 ml saline (0.9%), was injected as an i.v. bolus within 5 sec. For measurement of GH, ACTH and cortisol, blood was collected at -15, 0, 5, 15, 30, 60, 90 and 120 min. For determination of ACTH blood was drawn into prechilled tubes containing EDTA. The samples were immediately placed on ice, centrifuged at 4°C and 1000 X g for 15 min within 2 h of collection and the plasma stored at - 80 o C until analysed. Hormone
assays
GH levels were determined by a standard double-antibody RIA technique (INC, Stillwater, MN, U.S.A.). The detection limit was 0.5 ng/ml and the intra- and interassay coefficients of variation were 4% and 7%, respectively. ACTH was measured by radioimmunoassay after extraction and concentration on OctaDecaSilicaGel cartridges (Waters Assoc., Milford, MA, U.S.A.) using Nterminal specific antibodies (IgG Corp., Nashville, TN, U.S.A.) as previously described (Schulte et al., 1984). Cortisol was measured using a commercial radioimmunoassay (Immuchem Corp., Carson, CA, U.S.A.). Statistics
The results are expressed as the mean f SEM. Comparisons of baseline GH values were made by using the mean of the two basal values for each subject. The GH responses of patients and normal controls were calculated as the maximum increase above baseline (A ,,) in ng/ml and also as the integrated area under the response curve corrected for baseline (AUC) in ng . min/ml. GH responses were defined as positive only when both an increase to at least twice the baseline level and an absolute increase greater than 5 ng/ml were obtained (Linkowski et al., 1980). The data were analysed using nonparametric statistical methods; group comparison by the Mann-Whitney U-test; correlations by the Spearman’s rank order correlation (rs)_ All significance levels are two-tailed. Results
Compared with normal control subjects, pressed patients had a markedly exaggerated
deGH
response as assessed by the maximum GH increase above baseline (A,,,=: 5.5 f 1.1 vs. 12.2 k 3.8 ng/ml; U = 30, P -C 0.05) and by the integrated net area under the response’curve (AUC: 36.5 + 12.9 vs. 376.5 + 146.2 ng . mm/ml; U = 29, P < 0.05) (Fig. 1, Table 2). By the definition given above, in seven depressed patients (64%) a ‘paradoxical’ GH response to CRH was observed. Moreover, bipolar patients exhibited a greater ‘paradoxical’ GH output than the unipolar subsample, which was significant at the trend level (425.1 + 226.0 vs. 174.0 + 134.4 ng . mm/ml; U= 4, P -C 0.1). The exaggerated GH responses occurred in the face of normal GH baseline secretion (1.27 + 0.49 vs. 2.57 f 1.22 ng/ml; U= 52, NS). Although a positive correlation was found between basal plasma GH concentrations and net GH responses to CRH among normal controls (r, = 0.71, P < O.Ol), no significant relationship was found in the patient group (rs = 0.27, NS). No significant difference in the CRH-induced GH response was found between the patients receiving antidepressant therapy prior to the drug-free period of 3 days and the patients whose drug-free period exceeded 14 days. In contrast to normal subjects, depressed patients showed significantly attenuated net ACTH responses (1.2 + 0.1 vs. 0.6 + 0.1 X lo3 pg. mm/ml; U = 29, P < 0.05) and slightly reduced cortisol responses (7.9 + 1.3 vs. 5.0 + 1.7 x lo3 ng . min/ml; U = 41, NS) as as-
hCRH
TIME
(min)
Fig. 1. Plasma growth hormone (GH) secretion at baseline and following 100 pg human corticotropin-releasing hormone (hCRH) administered as an intravenous bolus at 6:OOp.m. in patients with major depressive disorder (symbols) and normal controls (shaded area).
248
TABLE
2
GH RESPONSE AFTER CRH STIMULATION PRESSIVE PATIENTS AND CONTROLS
Normal controls (n =ll) Depressed patients (n =ll)
Basal level
A max
(ng/ml)
(ng/nQ
1.3kO.5 2.6k1.2
h
5.5*1.1 12.2 f 3.8
IN
DE-
AUC a (ng.min/mI)
*
36.5k
12.9 *
316.5 + 146.2
a Area under the stimulation curve. ’ meankSEM * P < 0.05, Mann-Whitney U-test.
sessed by integration of the area under the stimulation curve. The blunted ACTH responses were associated with markedly elevated basal plasma cortisol concentrations (123.4 k 12.8 vs. 70.4 k 8.1 ng/ml; U = 21, P < 0.01). Basal secretion and net responses of ACTH and cortisol were not correlated with the basal GH secretion nor with the net GH responses in the two comparison groups. Discussion Our results demonstrate abnormal GH responses after CRH stimulation in association with normal basal plasma GH concentrations in patients with major depressive disorder. These data are in agreement with the findings of Gold et al. (1984) who also observed an increase in GH output in bipolar patients after administration of the long-acting ovine analogue of CRH. Although psychological stress has been shown to elevate plasma GH concentrations (Terry, 1984), our laboratory conditions did not elicit such a response in normal subjects. Since our experimental environment was free of stressful stimuli due to habituation procedures and was the same for both comparison groups, it is unlikely that nonspecific stress effects were responsible for an increased GH output after CRH in the depressed patients. The possibility that the abnormal GH responsiveness to CRH in depressed patients was related to the antidepressant treatment prior to the drug-free period should also be considered. However, no difference in the CRH-induced GH response was found between the patients who received antidepressant treatment before the drug-free period and
the patients who were off medication for a period exceeding 14 days. It is generally accepted that GH secretion is principally regulated by two hypothalamic peptides, growth hormone-releasing hormone (GHRH) (Rivier et al., 1982; Spiess et al., 1983) and somatostatin (Brazeau et al., 1973). Furthermore, CX-and P-adrenergic, dopaminergic, serotonergic, cholinergic and opioidergic innervation can modify GH secretory rates by acting on the central nervous system (CNS) to modulate the hypothalamic production of GHRH and somatostatin. GH release is also controlled by various peripheral hormones including glucocorticoids, thyroid hormones and somatomedins (Berelowitz et al., 1981; Vale et al., 1983). In addition, Rivier and Vale (1984) have shown that intracerebroventricular administration of ovine CRH to rats resulted in a dose-related inhibition of spontaneous GH secretion and, in contrast, intravenous injection was without effect. These findings indicate that CRH may act centrally to suppress the periodicity of spontaneous GH secretion, probably by inhibiting hypothalamic GHRH release, but is devoid of direct effects at the pituitary level. Since CRH penetrates the blood-brain barrier very poorly, the plasma CRH levels achieved during intravenous administration are probably not high enough to cause any major effect in the CNS. Moreover, CRH, which has been shown to stimulate somatostatin release, might further contribute to the inhibition of GH output in this way (Peterfreund and Vale, 1982). Evidently our study has complicated rather than clarified the role of CRH in the neuroregulation of GH release. In contrast to healthy subjects, who do not show a significant increase in GH output after CRH stimulation, paradoxical responsiveness of GH has been detected only in patients with acromegaly (Pieters et al., 1984) and in chair-restrained rhesus monkeys (Schulte et al., 1982). The abnormal GH rise in acromegaly has been attributed to dedifferentiation of receptors on GH-producing cells and/or to GHRH-induced sensitisation of pituitary somatotrophs (Borges et al., 1983). However, the mechanisms of stress-related increase of GH output after CRH in chairrestrained monkeys appear to be far more complicated. Schulte et al. (1982) demonstrated a sig-
249
nificant decrease of GH response to CRH by a-adrenergic, serotonergic and opioidergic blockade and concluded that CRH-induced GH secretion may be mediated by CRH-stimulated catecholamine or P-endorphin secretion and that CRH may play a coordinating role in sympathomimetic responses that occur during stress. While an enhanced catecholaminergic and opioidergic stimulation of GH release (M&i et al., 1984; Brown et al., 1985) most likely due to CRH-induced hypothalamic-pituitary-adrenal system hyperactivity (Lesch et al., 1987), needs to be confirmed in depressed patients, the common link with chair-restrained primates may be an augmented GHRH output due to increased cu-adrenergic activity. Moreover, a-adrenergic hyperactivity resulting in exaggerated GHRH release is consistent with the hypothesis of GHRH-induced sensitisation of somatotrophs (Borges et al., 1983) and with the recent observation of augmented spontaneous GH secretory bursts during the daytime in depressed patients (Mendlewicz et al., 1985). Therefore, we are tempted to speculate that the exaggerated GH output after CRH ultimately reflects abnormal neuroendocrine circadian rhythms associated with major depression (Pfohl et al., 1985). In summary, CRH stimulation demonstrated significant differences between depressed patients and healthy subjects involving several neuroendocrine systems. Evidently, these findings support the concept of heightened variability of neuroendocrine responsiveness in at least some subgroups of patients with affective illness. Acknowledgements The authors wish to express their gratitude to Dr. A.E. Jiirss and Mrs. Gross-Lesch for their assistance and help with the manuscript. References American Psychiatric Association Committee on Nomenclature and Statistics (1980) Diagnostic and Statistical Manual of Mental Disorders, 3rd edn., American Psychiatric Association, Washington, DC. Berelowitz, M., Szabo, M., Frohman, L.A., Firestone, S., Chu, L. and Hintz, R.L. (1981) Somatomedin-C mediates growth hormone negative feedback by effects on both the hypothalamus and the pituitary. Science 212, 1279-1281.
Borges, J.L.C., Uskavitch, D.R., Kaiser, D.L., Cronin, M.J., Evans, W.S. and Thomer, M.O. (1983) Human pancreatic growth hormone-releasing factor-40 (hpGRF-40) allows stimulation of GH release by TRH. Endocrinology 113, 1519-1521. Brazeau, P., Vale, W., Burgus, R., Ling, N., Butcher, M., Rivier, J. and Guillemin, R. (1973) Hypothalamic polypeptide that inhibits the secretion of immunoreactive pituitary growth hormone. Science 179, 77-79. Brown, M.R., Fisher, L.A. Webb, V., Vale, W. and Rivier, J.E. (1985) Corticotropin-releasing factor: a physiologic regulator of adrenal epinephrine secretion. Brain Res. 328, 355-357. Carroll, B. (1982) The dexamethasone suppression test for melancholia. Br. J. Psychiatry 140, 292-304. Chrousos, G.P., Schulte, H.M., Loriaux, D.L., Oldfield, E.H. and Gold, P.W. (1983) Corticotropin releasing factor: basic and clinical studies. Psychopharm. Bull. 19, 416-421. Gold, P.W., Chrousos, G., Kellner, C., Post, R., Roy, A., Avgerinos, P., Schulte, H., Oldfield, E. and Loriaux, D.L. (1984) Psychiatric implications of basic and clinical studies with corticotropin-releasing factor. Am. J. Psychiatry 141, 619-627. Hamilton, M. (1960) A rating scale for depression. J. Neurol. Neurosurg. Psychiatry 23, 56-62. Holsboer, F., von Bardeleben, U., Gerken, A., Stalla, G. and Mtiller, 0. (1984) Blunted corticotropin and normal cortisol responses to human corticotropin-releasing factor in depression. N. Engl. J. Med. 311, 1127. Lesch, K.P., Laux, G., Schulte, H.M., Pftller, H. and Beckmann, H. (1987) Corticotropin and cortisol response to human corticotropin-releasing hormone as a probe for hypothalamic-pituitary-adrenal system integrity in major depressive disorder. Psychiatr. Res. (in press). Linkowski, P., Brauman, H. and Mendlewicz, J. (1980) Growth hormone after TRH in women with depressive illness. Br. J. Psychiatry 137, 229-232. Loosen, P.T. and Prange, A.J. (1982) Serum thyrotropin response to thyrotropin-releasing hormone in psychiatric patients: a review. Am. J. Psychiatry 139, 405-416. Matussek, N., Ackenheil, M., Hippius, H., Miiller, F., Schriider, H.S., Schultes, A. and Wasilewski, B. (1980) Effect of clonidine on growth hormone release in psychiatric patients and controls. Psychiatr. Res. 2, 25-36. Mendlewicz, J., Linkowski, P., Kerkhofs, M., Desmedt, D., Golstein, J., Copinschi, G. and Van Cauter, E. (1985) Diurnal hypersecretion of growth hormone in depression. J. Clin. Endocrinol. Metab. 60, 505-512. Miki, N., Ono, M. and Shizume, K. (1984) Evidence that opioidergic and cr-adrenergic mechanisms stimulate rat growth hormone release via growth hormone-releasing factor (GRF). Endocrinology 114, 1950-1952. Peterfreund, R.A. and Vale, W.W. (1982) Ovine corticotropinreleasing factor stimulates somatostatin secretion from cultured brain cells. Endocrinology 112, 1275-1279. Pfohl, B., Sherman, B., Schlechte, J. and Stone, R. (1985) Pituitary-adrenal axis rhythm disturbances in psychiatric depression. Arch. Gen. Psychiatry 42, 897-903.
250 Pieters, G.F.F.M., Hermus, A.R.M.M., Smals, A.G.H. and Kloppenborg, P.W.C. (1984) Paradoxical responsiveness of growth hormone to corticotropin-releasing factor in acromegaly. J. Clin. Endocrinol. Metab. 58, 560-562. Rivier, C. and Vale, W. (1984) Corticotropin-releasing factor (CRF) acts centrally to inhibit growth hormone secretion in the rat. Endocrinology 114, 2409-2411. Rivier, J. Spiess, J., Thomer, M. and Vale, W. (1982) Characterization of a growth hormone releasing factor from a human pancreatic islet tumor. Nature (London) 300, 276. Schulte, H.M., Chrousos, G.P., Gold, P.W., Oldfield, E.H., Hoban, M.C., Cutler, Jr., G.B. and Loriaux, D.L. (1982) Corticotropin releasing factor (CRF): a common link between anterior pituitary and sympathetic response to stress. Acta Endocrinol. 253 (Suppl.), 32-33. Schulte, H.M., Chrousos, G., Avgerinos, P., Oldfield, E.H., Gold, P.W., Cutler, Jr., G.B. and Loriaux, D.L. (1984) The corticotropin-releasing hormone stimulation test: a possible aid in the evaluation of patients with adrenal insufficiency. J. Clin. Endocrinol Metab. 58, 106441066.
Spiess, J., Rivier, J. and Vale. W. (1983) Characterization of rat hypothalamic growth hormone releasing factor. Nature (London) 303, 532. Spitzer, R.L., Endicott, J. and Robins, E. (1978) Research Diagnostic Criteria (RDC) for a Selected Group of Functional Disorders. 3rd edn., New York State Psychiatric Institute, New York. Terry, L.C. (1984) Catecholamine regulation of growth hormone and thyrotropin in mood disorders. In: G.M. Brown (Ed.). Neuroendocrinology and Psychiatric Disorder, Raven Press, New York, pp. 237-254. Vale, W., Spiess, J., Rivier, C. and Rivier. J. (1981) Characterization of a 41-residue ovine hypothalamic peptide that stimulates secretion of corticotropin and /3-endorphin. Science 213, 1394-1397. Vale, W., Vaughan, J., Yamamoto, G., Spiess, J. and Rivier. J. (1983) Effects of synthetic human pancreatic (tumor) GH releasing factor and somatostatin, triiodo thryronine and dexamethasone in GH secretion in vitro. Endocrinology 112, 1553-1558.
of Affective
Disorders,
245
14 (1988) 245-250
Elsevier
JAD 00534
Abnormal responsiveness of growth hormone to human corticotropin-releasing hormone in major depressive disorder Klaus-Peter ’
Department
of Psychiatry, F.R.G.
and
Lesch’, Gerd Lauxl, Heinrich M. Schulte2, Hans Pfi.iller3 and Helmut Beckmann’
University of Wiirzburg, 8700
3 Department
of Endocrinology,
Wiirzburg, F. R.G., Pediatric
’ Department
of Medicine
Clinic, University of Wiirzburg,
8700
I, University of Kiel, 2300 Kiel, Wiirzburg,
F.R.G.
(Received 8 June 1987) (Revision received 16 November 1987) (Accepted 18 November 1987)
Summary Plasma growth hormone (GH) release after injection of 100 pg synthetic human corticotropin-releasing hormone (hCRH) was investigated in 11 patients with major depressive disorder and normal controls matched for gender, age, body weight and ovarian status. In contrast to controls, who exhibited no significant GH response to CRH, depressed patients showed a significant net increase in GH secretion following CRH administration. The abnormal GH response to CRH was not correlated with baseline corticotropin (ACTH) and cortisol nor with CRH-induced ACTH and cortisol response. The implications of these findings are discussed with reference to such factors as a-adrenergic hyperactivity, hypothalamicpituitary system dysregulation, drug interference, non-specific stress responses and abnormal neuroendocrine circadian rhythms in major depression.
Key words: Corticotropin-releasing
hormone; Growth hormone; Depression
A variety of neuroendocrine derangements have been described in association with major depression. These include failure to suppress cortisol after dexamethasone (Carroll et al., 1982) blunting of thyrotropin (TSH) response to thyrotropin-
Address for correspondence: Dr. K.-P. Lesch, Department of Psychiatry, University of Wiirzburg, Fkhsleinstrasse 15, 8700 Wiirzburg, F.R.G. 0165-0327/88/$03.50
0 1988 Elsevier Science Publishers
releasing hormone (TRH) (Loosen and Prange, 1982), attenuation of corticotropin (ACTH) after corticotropin-releasing hormone (CRH) stimulation (Gold et al., 1984; Holsboer et al., 1984; Lesch et al., 1987) and deficient growth hormone (GH) response to the a,-adrenoceptor agonist clonidine (Matussek et al., 1980). A more controversial finding is a ‘paradoxical’ GH response to TRH (Linkowski et al., 1980). However, more recent studies indicate that some depressives also show anomalous GH elevations after CRH (Gold et al., 1984).
B.V. (Biomedical
Division)
246
CRH, a 41-amino acid peptide isolated from the hypothalamus, is the primary neuroregulator of the secretion of pro-opiomelanocortin (POMC)derived peptides from the anterior pituitary (Vale et al., 1981). Although ‘paradoxical’ GH responses were reported in chair-restrained primates (Schulte et al., 1982) and in patients with acromegaly (Pieters et al., 1984) plasma GH levels were not influenced by the administration of CRH to healthy adults (Chrousos et al., 1983). The mechanisms underlying abnormal GH responses to CRH in depressed patients have not been clarified and a number of theoretical and methodological questions remain as to the nature and interpretation of ‘paradoxical’ GH output after CRH in major depression. The present investigation aimed to reassess patterns of plasma GH secretion after CRH in patients with major depressive disorder (both unipolar and bipolar) matched for gender, age, body weight and ovarian status with normal controls. Methods
TABLE
DATA
(MEAN + SEM)
Depressed (n=ll)
patients
Normal controls (12’11)
Age (years)
40.5 +4.6
(20-63)
Body weight (kg)
6X.X i 3.5
(52-8X)
Female Male
6 5
40.5 i 4.5 ( 19-64) 69.2 i 3.0 (52-90) 6 5
Age of onset of 1st depressive episode (years) Number of brevious affective episodes Duration of present depressive episode (months) Total duration of illness (years) Hamilton Depression SWVZ Time medication-free (days)
Subjects Eleven patients, six women and five men, fulfilled the requirements for major depressive disorder, endogenous subtype according to the Research Diagnostic Criteria (RDC) (Spitzer et al., 1978). The patients were diagnosed by two psychiatrists on the basis of a clinical interview using DSM-III (American Psychiatric Association, 1980) criteria. Seven patients were diagnosed as having a major depressive episode (MDE, without melancholia), the remaining four patients as having MDE with melancholia. Within the overall group of patients, seven were unipolar and four were bipolar patients. All investigations were performed after admission to the Department of Psychiatry, University of Wtirzburg. After given written informed consent, all patients were evaluated by physical examination and routine laboratory screening to exclude major physical disorder. Their ages were between 20 and 63 years (mean &- SEM = 40.5 _t 4.6 years), their body weights were 68.8 f 3.5 kg. of the six female patients five were post-menopausal. The study was performed after an average drug-free period of 9 days. In six patients the drug-free period exceeded 14 days;
1
DEMOGRAPHIC AND CLINICAL IN PATIENTS AND CONTROLS
35X24.4
(17-53)
3.0i0.42
(lm 6)
2.5kO.4
(l& 5)
4.7i1.4
(1-12)
25.5 f 1.1 (20-33) 9.051.7
(3-14)
< 5 -
five patients received amitriptyline, chlorimipra. mine, doxepine or mianserin prior to a drug-free period of 3 days. The 21-item Hamilton Rating Scale for Depression (HRSD) (Hamilton, 1960) was completed for each patient 1 day prior to the CRH test. Mean depression scale score was 25.5 f 1.1. Eleven normal controls (Table 1) were quadruple-matched for gender (five male, six female), age (40.5 + 4.5 years), weight (69.2 f 3.0 kg) and ovarian status (three pre-menopausal, three postmenopausal) and participated on a paid voluntary basis after written informed consent had been obtained. They reported no history of psychiatric disorders in first-degree relatives and none had taken any medication for at least 4 weeks before admission for study. They had refrained from alcohol use, were not sleep-deprived and were not involved in current stressful life events. Procedure The CRH stimulation tests were conducted on all subjects at rest in bed after a 6-h fast at 6:00
247
p.m. One hour after the insertion of an intravenous line in an antecubital vein, 100 pg synthetic human CRH (Bissendorf, Wedemark, F.R.G.), dissolved in 1 ml saline (0.9%), was injected as an i.v. bolus within 5 sec. For measurement of GH, ACTH and cortisol, blood was collected at -15, 0, 5, 15, 30, 60, 90 and 120 min. For determination of ACTH blood was drawn into prechilled tubes containing EDTA. The samples were immediately placed on ice, centrifuged at 4°C and 1000 X g for 15 min within 2 h of collection and the plasma stored at - 80 o C until analysed. Hormone
assays
GH levels were determined by a standard double-antibody RIA technique (INC, Stillwater, MN, U.S.A.). The detection limit was 0.5 ng/ml and the intra- and interassay coefficients of variation were 4% and 7%, respectively. ACTH was measured by radioimmunoassay after extraction and concentration on OctaDecaSilicaGel cartridges (Waters Assoc., Milford, MA, U.S.A.) using Nterminal specific antibodies (IgG Corp., Nashville, TN, U.S.A.) as previously described (Schulte et al., 1984). Cortisol was measured using a commercial radioimmunoassay (Immuchem Corp., Carson, CA, U.S.A.). Statistics
The results are expressed as the mean f SEM. Comparisons of baseline GH values were made by using the mean of the two basal values for each subject. The GH responses of patients and normal controls were calculated as the maximum increase above baseline (A ,,) in ng/ml and also as the integrated area under the response curve corrected for baseline (AUC) in ng . min/ml. GH responses were defined as positive only when both an increase to at least twice the baseline level and an absolute increase greater than 5 ng/ml were obtained (Linkowski et al., 1980). The data were analysed using nonparametric statistical methods; group comparison by the Mann-Whitney U-test; correlations by the Spearman’s rank order correlation (rs)_ All significance levels are two-tailed. Results
Compared with normal control subjects, pressed patients had a markedly exaggerated
deGH
response as assessed by the maximum GH increase above baseline (A,,,=: 5.5 f 1.1 vs. 12.2 k 3.8 ng/ml; U = 30, P -C 0.05) and by the integrated net area under the response’curve (AUC: 36.5 + 12.9 vs. 376.5 + 146.2 ng . mm/ml; U = 29, P < 0.05) (Fig. 1, Table 2). By the definition given above, in seven depressed patients (64%) a ‘paradoxical’ GH response to CRH was observed. Moreover, bipolar patients exhibited a greater ‘paradoxical’ GH output than the unipolar subsample, which was significant at the trend level (425.1 + 226.0 vs. 174.0 + 134.4 ng . mm/ml; U= 4, P -C 0.1). The exaggerated GH responses occurred in the face of normal GH baseline secretion (1.27 + 0.49 vs. 2.57 f 1.22 ng/ml; U= 52, NS). Although a positive correlation was found between basal plasma GH concentrations and net GH responses to CRH among normal controls (r, = 0.71, P < O.Ol), no significant relationship was found in the patient group (rs = 0.27, NS). No significant difference in the CRH-induced GH response was found between the patients receiving antidepressant therapy prior to the drug-free period of 3 days and the patients whose drug-free period exceeded 14 days. In contrast to normal subjects, depressed patients showed significantly attenuated net ACTH responses (1.2 + 0.1 vs. 0.6 + 0.1 X lo3 pg. mm/ml; U = 29, P < 0.05) and slightly reduced cortisol responses (7.9 + 1.3 vs. 5.0 + 1.7 x lo3 ng . min/ml; U = 41, NS) as as-
hCRH
TIME
(min)
Fig. 1. Plasma growth hormone (GH) secretion at baseline and following 100 pg human corticotropin-releasing hormone (hCRH) administered as an intravenous bolus at 6:OOp.m. in patients with major depressive disorder (symbols) and normal controls (shaded area).
248
TABLE
2
GH RESPONSE AFTER CRH STIMULATION PRESSIVE PATIENTS AND CONTROLS
Normal controls (n =ll) Depressed patients (n =ll)
Basal level
A max
(ng/ml)
(ng/nQ
1.3kO.5 2.6k1.2
h
5.5*1.1 12.2 f 3.8
IN
DE-
AUC a (ng.min/mI)
*
36.5k
12.9 *
316.5 + 146.2
a Area under the stimulation curve. ’ meankSEM * P < 0.05, Mann-Whitney U-test.
sessed by integration of the area under the stimulation curve. The blunted ACTH responses were associated with markedly elevated basal plasma cortisol concentrations (123.4 k 12.8 vs. 70.4 k 8.1 ng/ml; U = 21, P < 0.01). Basal secretion and net responses of ACTH and cortisol were not correlated with the basal GH secretion nor with the net GH responses in the two comparison groups. Discussion Our results demonstrate abnormal GH responses after CRH stimulation in association with normal basal plasma GH concentrations in patients with major depressive disorder. These data are in agreement with the findings of Gold et al. (1984) who also observed an increase in GH output in bipolar patients after administration of the long-acting ovine analogue of CRH. Although psychological stress has been shown to elevate plasma GH concentrations (Terry, 1984), our laboratory conditions did not elicit such a response in normal subjects. Since our experimental environment was free of stressful stimuli due to habituation procedures and was the same for both comparison groups, it is unlikely that nonspecific stress effects were responsible for an increased GH output after CRH in the depressed patients. The possibility that the abnormal GH responsiveness to CRH in depressed patients was related to the antidepressant treatment prior to the drug-free period should also be considered. However, no difference in the CRH-induced GH response was found between the patients who received antidepressant treatment before the drug-free period and
the patients who were off medication for a period exceeding 14 days. It is generally accepted that GH secretion is principally regulated by two hypothalamic peptides, growth hormone-releasing hormone (GHRH) (Rivier et al., 1982; Spiess et al., 1983) and somatostatin (Brazeau et al., 1973). Furthermore, CX-and P-adrenergic, dopaminergic, serotonergic, cholinergic and opioidergic innervation can modify GH secretory rates by acting on the central nervous system (CNS) to modulate the hypothalamic production of GHRH and somatostatin. GH release is also controlled by various peripheral hormones including glucocorticoids, thyroid hormones and somatomedins (Berelowitz et al., 1981; Vale et al., 1983). In addition, Rivier and Vale (1984) have shown that intracerebroventricular administration of ovine CRH to rats resulted in a dose-related inhibition of spontaneous GH secretion and, in contrast, intravenous injection was without effect. These findings indicate that CRH may act centrally to suppress the periodicity of spontaneous GH secretion, probably by inhibiting hypothalamic GHRH release, but is devoid of direct effects at the pituitary level. Since CRH penetrates the blood-brain barrier very poorly, the plasma CRH levels achieved during intravenous administration are probably not high enough to cause any major effect in the CNS. Moreover, CRH, which has been shown to stimulate somatostatin release, might further contribute to the inhibition of GH output in this way (Peterfreund and Vale, 1982). Evidently our study has complicated rather than clarified the role of CRH in the neuroregulation of GH release. In contrast to healthy subjects, who do not show a significant increase in GH output after CRH stimulation, paradoxical responsiveness of GH has been detected only in patients with acromegaly (Pieters et al., 1984) and in chair-restrained rhesus monkeys (Schulte et al., 1982). The abnormal GH rise in acromegaly has been attributed to dedifferentiation of receptors on GH-producing cells and/or to GHRH-induced sensitisation of pituitary somatotrophs (Borges et al., 1983). However, the mechanisms of stress-related increase of GH output after CRH in chairrestrained monkeys appear to be far more complicated. Schulte et al. (1982) demonstrated a sig-
249
nificant decrease of GH response to CRH by a-adrenergic, serotonergic and opioidergic blockade and concluded that CRH-induced GH secretion may be mediated by CRH-stimulated catecholamine or P-endorphin secretion and that CRH may play a coordinating role in sympathomimetic responses that occur during stress. While an enhanced catecholaminergic and opioidergic stimulation of GH release (M&i et al., 1984; Brown et al., 1985) most likely due to CRH-induced hypothalamic-pituitary-adrenal system hyperactivity (Lesch et al., 1987), needs to be confirmed in depressed patients, the common link with chair-restrained primates may be an augmented GHRH output due to increased cu-adrenergic activity. Moreover, a-adrenergic hyperactivity resulting in exaggerated GHRH release is consistent with the hypothesis of GHRH-induced sensitisation of somatotrophs (Borges et al., 1983) and with the recent observation of augmented spontaneous GH secretory bursts during the daytime in depressed patients (Mendlewicz et al., 1985). Therefore, we are tempted to speculate that the exaggerated GH output after CRH ultimately reflects abnormal neuroendocrine circadian rhythms associated with major depression (Pfohl et al., 1985). In summary, CRH stimulation demonstrated significant differences between depressed patients and healthy subjects involving several neuroendocrine systems. Evidently, these findings support the concept of heightened variability of neuroendocrine responsiveness in at least some subgroups of patients with affective illness. Acknowledgements The authors wish to express their gratitude to Dr. A.E. Jiirss and Mrs. Gross-Lesch for their assistance and help with the manuscript. References American Psychiatric Association Committee on Nomenclature and Statistics (1980) Diagnostic and Statistical Manual of Mental Disorders, 3rd edn., American Psychiatric Association, Washington, DC. Berelowitz, M., Szabo, M., Frohman, L.A., Firestone, S., Chu, L. and Hintz, R.L. (1981) Somatomedin-C mediates growth hormone negative feedback by effects on both the hypothalamus and the pituitary. Science 212, 1279-1281.
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