Immunohistochemical expression of Pit-1 protein in human pituitary adenomas.

Pit-1, the pituitary-specific transcriptional factor, has been known as a gene that regulates the functional differentiation of the anterior pituitary gland, especially in GH, PRL, and TSH production. Our immunohistochemical studies were performed to elucidate the functional roles of the pit-1 product in human pituitary adenomas. Eighty-six pituitary adenomas consisted of 51 GH-producing adenomas, 18 nonfunctioning (NF) adenomas, 1 1 PRL adenomas, and 6 TSH adenomas. Indirect immunoperoxidase method was performed using antibodies against GH, PRL, ACTH, the α subunit (SU), FSH β-SU, LH β-SU, TSH β-SU, and pit-1 product. Pit-1 product was expressed in 38 patients in the nuclei of the adenoma cells. The frequency of positive pit-1 product was significantly high in the patients with TSH and GH adenomas compared with those who had NF adenomas. These results suggest a role for pit-1 in functional differentiation of the human pituitary adenomas, especially TSH and GH adenomas.