Identification of gonadotropin-releasing hormone in neurons of a hypothalamic hamartoma in a boy with precocious puberty.

We have studied a 3 1/12-year-old boy who presented with a hypothalamic mass and precocious puberty. His history suggested a course of isosexual precocity progressing from birth. Gelastic seizures also began at an early age. Endocrine evaluation revealed normal thyroid-stimulating hormone and growth hormone secretion, elevated basal and stimulated prolactin concentrations, and luteinizing hormone responses to sequential intravenous injections of gonadotropin-releasing hormone (GnRH) that were pubertal in pattern and magnitude. A needle biopsy of the mass recovered tissue that contained neurons histologically similar to those found in the normal hypothalamus, and the mass was characterized as a hypothalamic hamartoma. Immunohistochemical staining of this tissue with anti-GnRH antiserum demonstrated positive staining for GnRH immunoreactivity in neurons. This suggests a neurosecretory pathogenesis for the precocious puberty found in patients with hamartomas in the hypothalamic region.