An Infant Case of Hyperprolactinemia Induced by a Functional Disorder of the Hypothalamus

Although functional hyperprolactinemia originating in the hypothalamus has been observed, there have so far been few reports of this condition occurring in children. This report describes a 1-yr-and-4-mo old boy with hyperprolactinemia due to functional disorder of the hypothalamic region. He was referred to our hospital because of left gynecomastia which had been observed for one month. His left breast development was stage II, right breast stage I, and pubic hair stage I by Tanner stages, and his bilateral testicular volume was 1 ml. Both his height and growth velocity were normal and his bone age was not advanced. The basal PRL level was high (40.4 ng/ml), but other sex steroids and adrenal androgen levels were normal. GnRH demonstrated the prepubertal stage. PRL response to TRH was normal and levodopa suppressed the increased basal PRL level. His chromosomal finding was 46, XY and macroprolactinemia was ruled out. Repeated MRI examinations did not demonstrate any organic lesions in the brain. He was diagnosed as having hyperprolactinemia induced by a functional disorder of the hypothalamus. His gynecomastia reduced and the high PRL level decreased without medication after 1 year.