Effects of growth hormone in Prader-Willi syndrome. A case report

C-reactive protein levels in subjects with Prader-Willi syndrome and obesity

PURPOSE

Prader-Willi syndrome is characterized by infantile hypotonia, feeding difficulties, hypogonadism, small hands and feet, mental deficiency, behavioral problems, and hyperphagia leading to obesity in early childhood. To date there have been no studies examining the associated risk of cardiovascular disease related to obesity in Prader-Willi syndrome, nor of circulating biomarkers such as C-reactive protein known to be predictive of cardiovascular disease. Therefore, we have measured the levels of C-reactive protein in a descriptive study of a cohort of Prader-Willi syndrome and comparison subjects.

METHODS

An immunoassay was used to quantify C-reactive protein in plasma samples from subjects with Prader-Willi syndrome and obesity and compared to anthropometric and body composition data.

RESULTS

The mean circulating C-reactive protein concentration for 28 subjects with Prader-Willi syndrome (13 females, 15 males; mean age 24.6 +/- 11.6 years; mean body mass index 35.9 +/- 11.9) was 10.3 +/- 8.8 mg/L. The mean C-reactive protein concentration for 22 nonsyndromic obese subjects (16 females, 6 males; mean age 32.3 +/- 12.2 years; mean body mass index 36.6 +/- 10.7) was 8.8 +/- 10.9 mg/L. The reported mean value for C-reactive protein was 2.6 +/- 3.0 mg/L from 100 healthy adults.

CONCLUSIONS

The mean C-reactive protein values were similar between the subjects with Prader-Willi syndrome and obesity but significantly higher in Prader-Willi syndrome and obese subjects relative to normative data. Increased levels of C-reactive protein (>3.0 mg/L) are associated with cardiovascular disease suggesting subjects with Prader-Willi syndrome as well as obese subjects are at a similar increased risk.

Growth hormone secretion in Prader-Willi syndrome

Prader-Willi Syndrome (PWS) is a multisystem defect characterized by obesity, hypogenitalism and short stature for genetic background. Low GH serum levels have been found in patients with PWS and were related to a hypothalamic-pituitary dysfunction. We studied spontaneous nocturnal GH secretion and GH-response to provocative tests in five patients affected by PWS. We observed in three of them (Group A) abnormally low GH and IGF-1 serum levels. In the other two patients (Group B) GH secretion and IGF-1 serum levels were normal. In all patients no thyroid dysfunction was observed. These data might suggest the presence of two different subgroups of patients affected by PWS, from an endocrinological point of view. An abnormally low GH secretion would be evident only in a subgroup of patients, which appears to be normal in the remaining patients. This casistic is small in number, but if our data will be confirmed by more extensive studies it may be possible to identify a specific population of PWS patients who could benefit from recombinant GH-therapy.

Reduced growth hormone (GH) responsiveness to combined GH-releasing hormone and pyridostigmine administration in the Prader-Willi syndrome

OBJECTIVE

It is unclear whether the blunted GH secretion in Prader-Willi Syndrome (PWS) is a true deficiency, or merely secondary to obesity. We have investigated the role of obesity in the blunted GH secretion in PWS.

DESIGN

We studied the GH response to a combined administration of GHRH (1 microgram/kg i.v. at 0 min) and pyridostigmine (PD) (60 and 120 mg by mouth for children and adults, respectively, at time -60 min), as well as the baseline IGF-I levels, in a group of patients with PWS. Two different control groups were studied with GHRH + PD using the same doses and methods as above: prepubertal and pubertal obese subjects, and prepubertal short normal children. Moreover, in 14 patients with PWS and in the group of short normals the GH response to at least two stimulation tests (insulin tolerance test, clonidine, L-dopa, arginine) had been previously determined.

PATIENTS

Twenty-two PWS patients (10 males and 12 females), 21 with essential obesity (11 males and 10 females), and eight short normal children (4 males and 4 females) were studied after obtaining informed consent.

MEASUREMENTS

Blood samples were taken at -60, -30 and 0 min and then 15, 30, 45, 60, 90 and 120 min after GHRH administration. Serum GH was measured in duplicate by IRMA, and IGF-I by RIA after acid ethanol extraction. Statistical analysis was performed by t-test for unpaired data, and analysis of variance for parametric or nonparametric data, where appropriate.

RESULTS

The GH response to GHRH + PD was significantly lower in PWS patients (AUC: mean +/- SE: 599 +/- 99 micrograms/l/h) if compared with either short normal children (3294 +/- 461 micrograms/l/h: P < 0.0001) or obese subjects (1445 +/- 210 micrograms/l/h: P < 0.005). Low IGF-I concentrations were found in all PWS patients, so that PWS group had mean IGF-I levels significantly lower than the other groups.

CONCLUSIONS

Our results showed that subjects with PWS had a reduced GH responsiveness to GHRH + PD associated with subnormal IGF-I levels. These findings suggested that short stature in PWS may be at least partially correlated to the presence of GH deficiency, and that impaired GH secretion is not secondary to obesity.

Effect of growth hormone on height, weight, and body composition in Prader-Willi syndrome

AIMS

To evaluate the effect of the administration of growth hormone on stature, body weight, and body composition in children aged between 4 and 10 years with Prader-Willi syndrome.

METHODS

Height, weight, and skinfold thickness were recorded in 25 children using standard anthropometric techniques at recruitment, and six months later, shortly before the start of daily subcutaneous injections of growth hormone. Body composition was assessed via a measurement of total body water using stable isotopes. Measurements were repeated at the end of the six months of growth hormone administration. Measurements of height, weight, and skinfold thickness were expressed as standard deviation scores (SDSs).

RESULTS

There was a significant reduction in the percentage of body fat after growth hormone treatment; height velocity doubled during treatment; body weight did not change significantly when expressed as an SDS. Skinfold thickness at both the triceps and subscapular site decreased in absolute terms and when expressed as an SDS.

CONCLUSIONS

These results indicate sufficient potential benefit to justify a more prolonged trial of growth hormone treatment and an exploration of different dosage regimens in children with Prader-Willi syndrome.

Treatment with human growth hormone in patients with Prader-Labhart-Willi syndrome reduces body fat and increases muscle mass and physical performance

Twelve children with documented Prader-Labhart-Willi syndrome were treated with human growth hormone (24 U/m2/week) during 1 year. The children were divided into three groups: group 1: overweight and prepubertal (n=6, age 3.8-7.0 years); group 2: underweight and prepubertal (n=3, age 0.6-4.1 years); group 3: pubertal (n=3, age 9.2-14.6 years). In group 1, height increased from -1.7 SD to -0.6 SD, while weight decreased from 1.1 SD to 0.4 SD, with a dramatic drop in weight for height from 3.8 SD to 1.2 SD. Hand length increased from -1.5 SD to -0.4 SD and foot length from -2.5 SD to -1.4 SD. Body fat, measured by dual X-ray energy absorptiometry, dropped by a third, whereas muscle mass increased by a fourth. Physical capability (Wingate test) improved considerably. The children were reported to be much more active and capable. In group 2, similar changes were seen, but weight for height increased, probably because muscle mass increase exceeded fat mass decrease. Changes in group 3 were similar as in group 1, even though far less distinct.

CONCLUSION

Growth hormone treatment in Prader-Labhart-Willi syndrome led to dramatic changes: distinct increase in growth velocity, height and muscle mass, as well as an improvement in physical performance. Fat mass and weight for height decreased in the initially overweight children, and weight for height increased in underweight children.

Effect of 6 months of growth hormone treatment in young children with Prader-Willi syndrome

Nine prepubertal children with Prader-Willi syndrome were treated with growth hormone (GH; 24 IU/m2/week) for 6 months. Mean height increased by 0.8 SD and mean weight for height decreased by 0.7 SD over this 6-month treatment period. Body fat, measured by dual-energy X-ray absorptiometry, decreased by 22.5% over the period of GH treatment, whereas fat-free mass increased by 14%. These preliminary results indicate that GH is effective in increasing height and normalizing body composition in patients with Prader-Willi syndrome.

Impairment of growth hormone responsiveness to growth hormone releasing hormone and pyridostigmine in patients affected by Prader-Labhardt-Willi syndrome

In order to evaluate the impairment of GH response in patients affected by Prader-Labhardt-Willi (PLW) syndrome, in 18 patients we studied GH response to clonidine and to GHRH + pyridostigmine, a cholinergic drug which enhances GHRH induced GH responsiveness in obese patients. After clonidine GH response was abnormal in 14/18 subjects (mean GH peak: 4.1 +/- 1.3 micrograms/l; area under curve: 208.1 +/- 74.2 micrograms/l.h) while all but 5 patients showed an inadequate GH response to GHRH + pyridostigmine (mean GH peak: 13.4 +/- 2.5 micrograms/l; area under curve: 903.4 +/- 171.0 micrograms/l.h). However, in the three patients with low adiposity index, GH response to GHRH + pyridostigmine was significantly higher than that observed in fatter subjects. In addition, GH response to GHRH + pyridostigmine was negatively correlated to age and adiposity index. In conclusion, our data are consistent with the hypothesis of the existence of a complex derangement of GH neuroendocrine regulation in these subjects.

Growth hormone secretion and effects of growth hormone therapy on growth velocity and weight gain in children with Prader-Willi syndrome

Obesity, short stature, decreased growth rate and delayed skeletal maturation are common features of children with Prader-Willi syndrome (PWS). In contrast to PWS, children with simple exogenous obesity have normal or increased growth rate and normal or advanced skeletal maturation. Decreased growth hormone (GH) secretion evaluated by pharmacological or physiological testing associated with increased plasma insulin-like growth factor (IGF-I) and GH-binding protein (GH-BP) levels are also characteristic of simple obesity. In order to understand whether the suboptimal GH secretion in PWS is an artifact of the obesity, we studied 33 obese and 11 non-obese PWS children, aged 2-16 years.GH secretion was evaluated with three pharmacological stimuli (insulin, clonidine and L-dopa) and by spontaneous 24-hour GH secretion. Skeletal maturation was delayed in 70% whereas plasma IGF-I and GH-BP were either low or normal. Forty subjects, including ten non-obese children, had GH deficiency by standard testing (failure to respond to two pharmacological stimuli), and all but one had blunted spontaneous 24-h GH secretion. No significant correlation between body mass index (wt/ht2) and spontaneous 24-h GH secretion (r = 0.145), p > 0.06) or GH-BP levels (r = 0.19, p > 0.07) was found. Thirty documented GH deficient children have completed at least two years of GH therapy. With treatment the overall mean height SD and weight SD changed from -2.2 to -0.8 and from 3.5 to 2.4 respectively (p < 0.0001). No patient has developed diabetes mellitus. In conclusion, growth velocity, skeletal maturation, GH secretion and GH dependent proteins in PWS resemble GH deficiency more than simple obesity. Our ongoing study suggests that GH deficiency in PWS is not an artifact of obesity. Although it is unlikely that GH deficiency is the only cause of decreased growth velocity and increased adiposity in PWS, it is a common feature and significant contributory factor. Long term observation will be required until achievement of adult height to determine whether GH therapy actually improves final height.

MR of the pituitary in patients with Prader-Willi syndrome: size determination and imaging findings

Prader-Willi syndrome (PWS) is an unusual genetic disorder characterized by short stature, obesity, hypogonadism, hypotonia, cognitive impairment, and dysmorphic facies. There is an interstitial deletion of the proximal long arm of chromosome 15 in about 70 % of patients. Some of these clinical features suggest a central hypothalamic/pituitary dysfunction, and recent investigations have demonstrated a marked impairment in spontaneous growth hormone (GH) secretion. We studied 15 GH-deficient PWS patients by magnetic resonance imaging (MRI) to determine whether there was a diminution in the gross morphological size of the anterior pituitary gland, the site of GH synthesis. We also set out to catalog the pertinent imaging findings in this patient population. Our results indicate that this is the first report documenting pituitary size by MRI in PWS patients. No statistically significant difference was found in the height of the anterior pituitary gland in PWS patients compared with either normal children or children with isolated GH deficiency. An interesting imaging finding is that three of 15 patients (20 %) demonstrated complete absence of the posterior pituitary bright spot (PPBS), and a fourth patient demonstrated a small PPBS. These observations reflect an objective physiologic disturbance in the hypothalamus. The clinical and radiologic implications of these findings are discussed.