Hereditary pituitary prolactinomas: a new rat model

Pituitary adenomas are known to occur spontaneously in several rat strains, especially during aging. Here we report the occurrence of adenomas (prolactinomas) in a new rat model at an early age. The adenomas were characterized by light and electron microscopy and histochemically by immunoperoxidase methods using specific antisera. Of the 53 pituitaries examined, one was normal, two were hyperplastic and the remainder were adenomas. Among the latter, there were 37 prolactinomas (70%), 3 GH-producing tumours and 2 ACTH-containing neoplasms. One microadenoma produced both PRL and GH. The remaining 8 adenomas were histochemically negative for all pituitary hormones. Serum PRL levels were elevated in both sexes while serum testosterone was high in females and low in the males. The serum estrogen levels were elevated in the males with prolactinomas. The prolactinomas appear to be transmitted as an autosomal dominant characteristic with incomplete penetrance and a greater incidence in the male.