Growth hormone excess and sexual precocity in polyostotic fibrous dysplasia (McCune-Albright syndrome): evidence for abnormal hypothalamic function.

A 5-5/12-year-old boy with gigantism and precocious puberty associated with the McCune-Albright syndrome is presented. Serum concentrations of growth hormone were extremely elevated (128-163 ng/ml) and were not suppressed by hyperglycemia or chlorpromazine. Serum LH (7.4 +/- 1.0 SD mIU/ml) and FSH (5.3 +/- 0.3 SD mIU/ml) concentrations were in the range observed in midpuberty. The secretion pattern of LH was episodic. The administration of estradiol suppressed the secretion of FSH and had an apparent positive feedback effect on release of LH. These findings are compatible with abnormal hypothalamic function as the mechanism for the endocrinopathies associated with the McCune-Albright syndrome.