Growth hormone secretion in Prader-Willi syndrome.

Integrated 12-hour growth hormone secretion studies, peak growth hormone response to clonidine provocation. Somatomedin-C levels, T-4 and TSH levels were studied in six growth-retarded children with the Prader-Willi syndrome, of whom five had a 15 q-karyotype. Only one of the subjects was obese. All showed abnormally low growth hormone secretion. None achieved a nocturnal peak above 10 micrograms/l, none had a mean nocturnal level over 1.8, and none showed a level above 8 micrograms/l after clonidine provocation. These findings contrasted with normal TSH in all and normal T-4 in five. These findings suggest that the poor linear growth in the Prader-Willi syndrome is caused by a true deficiency of growth hormone secretion, and that the low growth hormone levels observed in such cases are not an artifact of obesity.