Lack of clinical evidence of sodium retention in children with idiopathic short stature treated with recombinant growth hormone

Lack of Clinical Evidence of Sodium Retention in Children With Idiopathic Short Stature Treated With Recombinant Growth Hormone Joan DiMartino-Nardi,

Susan Wesoly,

Lisa Schwartz,

and Paul Saenger

In adult patients, administration of human growth hormone and growth hormone synthesized by recombinant DNA technology (rGH) results in sodium and fluid retention and weight gain. This study was performed to determine whether rGH administration in children with idiopathic short stature (ISS) caused any clinical evidence of sodium retention. The parameters assessed included blood pressure, height, weight, plasma renin activity (PRA), aldosterone, and atrial natriuretic peptide (ANP). These were measured in nine treated children after 0, 3, 6, 9, and 12 months of growth hormone therapy; seven untreated children served as controls. After 12 months, the treated children had no significant increases in measurements of blood pressure, PRA, aldosterone, and ANP. Although treated children gained more weight than control patients, they also grew faster. Therefore, there was no significant difference in weight for height percentile for treated children when compared with normal controls. After 1 year of therapy, the administration of rGH to children with ISS does not result in any clinically significant evidence of sodium retention. Copyright 0 1993 by W.B. Saunders Company

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N ADULT PATIENTS, administration of human growth hormone and growth hormone synthesized by recombinant DNA technology (rGH) can be associated with sodium and fluid retention and weight gain.‘-” In the past, the limited supply of pituitary-extracted growth hormone restricted its distribution to growth hormone-deficient children. Advances in recombinant DNA technology have made growth hormone readily available for the treatment of children with growth hormone deficiency. Currently, investigations are under way to assess its effect on stature in healthy non-growth hormone-deficient children with idiopathic short stature (ISS).12 Short-term administration of rGH results in sodium and fluid retention.*3J4 Clinically mild and transient edema has been observed in 2.5% of patients early in the course of treatment with rGH.15 This study was performed to determine whether longterm administration of rGH to healthy children with ISS results in any clinical evidence of sodium retention.

mouth), glucagon (0.1 mg/kg intramuscularly), or L-DOPA (< 14 kg, 125 mg by mouth; 14 to 30 kg, 250 mg by mouth; > 30 kg, 500 mg by mouth). Of these 16 children, nine were randomly chosen to be treated with rGH at a dosage of 0.1 mgikg subcutaneously triweekly; seven children did not receive therapy and were followed as controls. The mean age of treated children at the start of the study was 9.9 + 1.4 years, and the mean age of untreated children was 9.3 ? 2.7 years. Treated children were seen at 3,6,9, and 12 months after initiation of growth hormone therapy. Untreated children were seen at 0,6, and 12 months of study. At each visit, the following parameters were measured: height, weight, and blood pressure. Plasma renin activity (PRA), aldosterone, and atria1 natriuretic peptide (ANP) levels were measured in all treated children and four untreated children. Height was measured three times at each visit using a Harpenden Stadiometer (Seritex, Inc, Carlstadt, NJ). Blood pressure was measured three times at each visit using mercury sphygmomanometers. Weight for height was calculated from tables published by the National Center for Health Statistics.18

Laboratory Methods SUBJECTS AND METHODS

Patient Population Sixteen healthy children with ISS were included in the study; these patients also participate in an ongoing evaluation of the effect of growth hormone therapy in children with 1SS.12 The criteria for enrollment included a height of more than 2.5 standard deviations below the mean for chronological age; a growth velocity less than the 50th percentile for age’$ a bone age in boys of less than 10 years and in girls of less than 9 years (as assessed using the method of Greulich and Pyle)17; and a growth hormone response of greater than 10 ng/mL to standard provocative testing after either 20 minutes of exercise or administration of clonidine (0.1 mg by

From the Depatiment of Pediatrics, Division of Pediatric Endocrinology, Montefore Medical CenterlAlbeti Einstein College of Medicine, New York, NY Submitted March 19, 1992; accepted Jux 18, 1992. Supported by a grant-in-aidfrom Genentech, South San Francisco, CA. Address reprint requests to Joan DiMartino-Nardi, MD, Department of Pediatrics, Montejore Medic& Center, 111 E 210th St, New York, NY10467. Copyright 0 1993 by W. B. Saunders Company 0026-0495i9314206-‘0011$03.00i0 730

ANP level was measured using a radioimmunoassay from the Nichols Institute (San Juan Capistrano, CA). An antiserum developed in rabbits against l-28 human ANP was used. Plasma samples were extracted using a Sep-Pak C-18 column (Water’s Associates, Milford. MA), and the extracted samples were assayed by the sensitive radioimmunoassay (10 pg/mL at 90% Be/B [bound/ free]). Bound/free separation was achieved using goat anti-rabbit y-globulin second-antibody separation procedures. The crossreactivity of anti-ANP with ANP and related polypeptides is as follows (presented as peptide, RIA reactivity): (a)hANH (l-28aa), 100%; (a, y)ANH (l-28aa), 43%; (y)atriopeptin I (5-25aa), 1%; (y)atriopeptin II (5-27aa), 0.2%; (y)atriopeptin III (5-28aa), 0.1%; and (y)atriopeptin (13-28aa), 0.0%. Intraassay and interassay coefficients of variation were 8.4% and 13.1%, respectively (normal expected values are 25 to 77 pg/mL). Radioimmunoassay of aldosterone was performed after methylene chloride extraction and purification through celite chromatography (Nichols Institute). The percent recovery was 85%. and intraassay and interassay coefficients of variation were 10% and 13%, respectively (normal expected values are 4 to 4.5 ng/dL for upright adults on a normal-salt diet). PRA was determined by a radioimmunoassay of angiotensin performed after incubation of plasma for 1 hour at 37°C (Nichols Institute). Intraassay and interassay coefficients of variation were 9.1% and 12.2%, respectively (normal values for standing adults are 4.5 ? 2.9 ng/mL/h). Metabolism,

Vol42,

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RETENTION

Results were analyzed using Student’s t test. P values less than .05 were considered to indicate statistical significance. RESULTS

Growth velocities for treated and untreated children are shown in Fig 1. After 1 year, growth velocities (mean ? SD) for treated children increased from 3.8 ? 1.5 to 6.9 t 0.8 cm/y. The growth velocity for untreated children was 4.8 2 1.2 cm/yr, and it remained at 5.3 f 0.8 cmiyr after 1 year of observation. After 1 year, treated children grew significantly faster than untreated children (P < .05). Treated children gained 3.8 ?z 1.4 kg during the year, which is an amount greater than that of untreated children, who gained 2.7 f 0.5 kg. In Fig 2 are plotted the weight for height percentiles of the seven rGH-treated and four untreated children. In treated children at 0, 3, 6, 9, and 12 months the weight for height percentiles (mean *SE, range in parentheses) were 45.4 t 8.4 (584), 42.7 2 7.3 (10-81) 46 4 -+ 8.4 (8-85) 48.2 2 6.5 (23-83) and 52.2 c 7.5 (12-85) respectively. For the seven untreated children, the weight for height percentiles were 57.7 t 9.0 (13.6~86), 57.1 % 7.5 (22.3-80), and 62.6 t 7.0 (2583.0) at 0,6, and 12 months of study, respectively. There was no significant increase in weight for height in either group by 12 months of study. Although the treated children gained more weight, they also grew more; therefore, the weight for height percentiles remained the same in both groups. Figure 3 shows the children’s mean blood pressures during the study. In treated children, blood pressures expressed as mean systolic/diastolic mm Hg 2 SD (range) were 97/68 t 5.8/7.4 (90-110/58-70); 90157 2 7.3/5.0 (80-104/50-62); 97/63 * 10.3/8.1 (82-110,‘51-80); 94/62 ? 84’4.0 (80-108/58-70); and 95/61 ? 9.3/3.4 (90-110/58-70) at ,1, 3, 6, 9, and I2 months of study, respectively. For untreated children, blood pressures were 97.4/58.9 -t 12.9/8.5 (88-120/50-72); 91.5/57 2 9.1/3.9 (84-110/50-60); and 89.4J56.9 ? 6.8J7.0 (90-96/48-70) at 0, 6, and 12 months of study, respectively. Blood pressures of children in both groups remained the same. PRA is presented in Fig 4. For treated children, PRA expressed as mean t SE (range) was 4.3 +- 0.6 (2.3-8.3); 4 5 -t 0.7 (1.7-8.9); 6.6 + 0.5 (4.2-8.3); 3.9 r 0.8 (0.8-8.6);

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Fig 2. Weight for height percentiles in nine rGH-treated and untreated children at 0.6, and 12 months of study. Weight for height percentiles remained the same in both groups throughout the study.

and 3.5 ? 0.7 (1.0-6.4) ng angiotensinlmlih at 0, 3, 6, 9, and 12 months of study, respectively. PRA for untreated children was 4.6 it 0.6 (3.1-6.2); 4.9 ? 0.9 (3.3-7.0); and 5.2 + 0.7 (3.6-6.6) ng angiotensin/mL/h at 0, 6, and 12 months of study, respectively. PRA remained the same in both groups. Aldosterone levels are shown in Fig 5. In treated children, aldosterone levels (mean t SE [range]) were 9.0 ? 2 (3-23); 9 ? 1(3-18); 17 2 5 (5-51); 10 ? 3 (3-26); and 14 2 3 (2-31) ng/dL at 0, 3, 6, 9, and 12 months of study, respectively. For untreated children, aldosterone levels remained at 4 * 0.8 (2-5); 7 t 2 (2-10); and 9 2 5 (2-21) ng/dL at 0, 6, and 12 months. Aldosterone levels remained the same in both groups throughout the entire study period. ANP levels are compared in Fig 6. In treated children, ANP levels (mean -t SE [range]) were 55 t 14 (18-168); 52 2 8 (22-100); 47 ? 4 (30-65); 53 * 9 (31-115); and 58 & 15 (25-136) pg/mL at 0,3,6,9, and 12 months, respectively. In untreated children, ANP levels remained at 51 2 7 (30-66); 52 2 8 (33-65); and 54 t 12 (22-87) pg/mL at 0,6, and 12 months. There were no changes in ANP levels in rGH-treated children after 1 year of therapy. DISCUSSION

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Fig 6. ANP levels (mean + SE) in rGH-treated and untreated patients at 0,3,6,9, and 12 months of study. There were no changes in ANP levels in treated patients after 1 year of therapy.

tors. The administration of pituitary-derived growth hormone to animals resulted in an increase in total body water and plasma volume.6 In 1953, Ikkos et al’ demonstrated that acromegalics had an increase in total body water and total exchangeable sodium. Several studies demonstrated that short-term administration of human growth hormone to adults with and without growth hormone deficiency resulted in sodium retention and weight gain.7-9 The mechanism of sodium retention remained an enigma; it was suggested that the presence of antidiuretic activity (not identified by routine assays at that time) was responsible for these observations. Similarly, the administration of human growth hormone to hypopituitary children for 1 year resulted in an increase in total body water.lO Weight reduction was observed initially in overweight patients; in other patients, weight increments were observed. Rifkind et al” also observed that short-term administration of human growth hormone (5 days to 1 week) to growth hormone-deficient children resulted in an increase in total body water. In some of these patients, long-term (6 weeks to 1 year) administration of human growth hormone also resulted in an increase in total body water. Information regarding the long-term effect of growth hormone on the weight of these children was not included. Again, neither corticotropin nor antidiuretic hormone were detected in the human growth hormone preparation used. It was

speculated that sodium retention reflected an intrinsic property of the growth hormone molecule or an action of a minor contaminant. Studies are now under way to assess the growthpromoting effect of rhGH in short non-growth hormonedeficient children (children with ISS), its anabolic effect during treatment of patients with critical illnesses such as injury or infection, its lipolytic effect in obese subjects, and its effect on lean body mass and adipose tissue in aging men. In obese subjects, rGH at doses of 0.1 mg/kg body weight has been used to determine whether it can accelerate the loss of body fat during dietary restriction.19 Unfortunately but interestingly, weight loss was attenuated because of fluid retention during both short- and long-term trials of rGH. Furthermore, when rGH was discontinued, the patients entered a period of increased diuresis, suggesting that the large doses of rGH resulted in fluid retention. Fluid retention also was observed when rhGH at doses of 10 mg/d was administered to men on hypocaloric feedings to assess the effect of growth hormone on nitrogen retention.*O In six of 24 treated adults with growth hormone deficiency, fluid retention was observed after 1 month of therapy with rGH. Symptoms included an increase in body weight, swollen ankles, and a sensation of tightness in the hands.*’ In a recent report, growth hormone was administered to aging men to assess its effect on lean body mass and adipose tissue.22 After 6 months of therapy, no edema was observed, but there was a significant increase in mean systolic blood pressure. Recently, studies have been performed to assess the short-term effect of growth hormone administration on sodium metabolism. Administration of biosynthetic growth hormone at a dose of 0.2 U/kg/d for 5 consecutive days in six healthy adult men resulted in clinical and biochemical evidence of sodium retention that was marked by weight gain, a reduction of urine volume and urinary sodium excretion, and an increase in PRA and aldosterone levels.‘” The investigators expressed concern that administration of growth hormone to children with ISS would cause fluid retention and result in expanded plasma volume and hypertension, as occurs in acromegaly. In Moller’s study, administration of growth hormone to eight men at the high

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dose of 12 IU daily for 14 days resulted in an increase in extracellular volume and a significant suppression of ANP.14 In a study of the effect of exogenous biosynthetic growth hormone on sodium metabolism in children with growth hormone deficiency, it was noted that before therapy, growth hormone-deficient, children had systolic blood pressures and serum aldosterone levels lower than those of control non-growth hormone-deficient patients.*” With slort-term administration of biosynthetic growth hormone at a dose of 0.4 IU/kg/wk divided daily for 1 month, systolic blood pressures and aldosterone levels increased to levels similar to those of controls; there was no change in PRA or ANP leveis. This study was performed to determine whether the current doses of rGH administered to healthy children with 1% resulted in any clinical evidence of sodium retention. &though others have reported edema in their patients in tially (first few weeks of therapy), no edema was observed in our patients. The sodium retention observed in adults may be the result of the higher dose used. Our treated children had a significant increase in growth velocity; although these children gained weight. their weight for height percentile remained the same after 1 year of treatmcnt. Furthermore, the treated children had no significant changes in blood pressure, PRA, and aldosterone and ANP levels. In this cohort of children. although aldosterone levels were higher in the treated group at all times, the difFerencc between treated and untreated children at 0, 6, and 12 months was not statistically significant. At 6 months.

for unexplained reasons, one treated patient had an aldosterone level that was markedly elevated to 51 ng/dL. When this patient’s aldosterone level was excluded from the calculations, the mean 6-month aldosterone level for treated children was 13.2 (5-28 ng/dL). Furthermore, by 9 months of treatment, the aldosterone level in the same patient decreased to 4 ng/dL. Therefore, at this time, we arc reluctant to speculate on the significance of elevated mean aldosterone levels observed in treated patients. We chose to measure the level of ANP. as it has an important role in sodium and fluid homeostasis.z4Js Levels of ANP have been found to be altered in patients with renal failure. hypothyroidism, and Cushing’s syndrome-disorders associated with an increase in extracellular fluid volume.zh-z* In our patients, ANP levels remained normal throughout the study period and were not different from those of untreated patients. Therefore, after 12 months of therapy, although growth hormone did have a therapeutic effect on growth, it did not provoke any clinical or biochemical evidence of sodium retention. Recombinant DNA technology has increased the availability of rGH for the treatment of healthy short children. Additional studies are warranted to define the long-term effect of growth hormone on sodium and fluid balance in these children. ACKNOWLEDGMENT We thank Lorraine Miller for preparation Kenneth Fishman for technical assistance.

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