Growth hormone secretion in Prader-Willi syndrome

Area of Science:

• Pediatric Endocrinology
• Genetics
• Metabolic Disorders

Background:

• Prader-Willi syndrome (PWS) is a complex genetic disorder often associated with growth retardation.
• The etiology of growth failure in PWS, particularly concerning growth hormone (GH) secretion, requires clarification.

Purpose of the Study:

• To investigate the integrated 12-hour GH secretion and GH response to clonidine provocation in children with PWS.
• To assess Somatomedin-C, thyroxine (T-4), and thyroid-stimulating hormone (TSH) levels in these patients.
• To determine if GH deficiency is the primary cause of poor linear growth in PWS.

Main Methods:

• Six growth-retarded children with PWS (five with 15q-karyotype) underwent integrated 12-hour GH secretion studies.
• Clonidine provocation tests were performed to assess peak GH response.
• Serum levels of Somatomedin-C, T-4, and TSH were measured.

Main Results:

• All subjects demonstrated abnormally low integrated GH secretion, with no nocturnal peak above 10 µg/L and a mean nocturnal level under 1.8 µg/L.
• None achieved a GH level above 8 µg/L after clonidine provocation.
• Thyroid function tests were normal in most subjects (normal TSH in all, normal T-4 in five), contrasting with the impaired GH secretion.

Conclusions:

• The findings strongly suggest a true deficiency in GH secretion as the cause of poor linear growth in PWS.
• The observed low GH levels in PWS are not an artifact of obesity, as only one subject was obese.