Precocious puberty and hypothalamic hamartoma.

A 3-year-old boy with true precocious puberty and hamartoma of the hypothalamus is described. Preliminary diagnosis was established by the presence of unusually advanced puberty and skeletal age without other evidence of central nervous system dysfunction, elevated blood gonadotropin and testosterone concentrations, and positive computed tomography scans. Pneumoencephalography further delineated the tumor. Hypothalamic-pituitary-gonadal and adrenal functions were studied. Release of gonadotropins after the injection of synthetic luteinizing hormone-releasing hormone and the suppression of luteinizing hormone and of testosterone by oral fluoxymesterone were comparable to maximal responses of normal men. The diagnosis was confirmed by histologic and electron microscopic study of an excised portion of the tumor. Immunofluorescence studies indicated the presence of luteinizing hormone-releasing hormone in the hamartoma and radioimmunoassays detected thyroid-stimulating hormone-releasing hormone and somatostatin. The hamartoma resembles an autonomously functioning accessory hypothalamus. The ectopic neuroendocrine pathways, however, are responsive to hormonal stimulation and feedback. The clinical, endocrinologic, and pathologic features of published cases of precocious puberty and hypothalamic hamartoma are reviewed. Advanced or rapidly progressive true precocious puberty in the very young with elevated concentrations of blood gonadotropins and gonadal steroids and positive pneumoencephalography appear to be characteristic.