Effects of thyrotropin-releasing hormone and gonadotropin-releasing hormone on inositol phospholipid turnover in endocrinologically inactive pituitary adenomas and prolactinomas.

We examined the effects of GnRH and TRH on inositol phospholipid turnover in 11 endocrinologically inactive pituitary adenomas and 5 prolactinomas. In 9 of the 11 nonsecreting adenomas, GnRH induced a significant increase in inositol phospholipid turnover; of those that responded, increased inositol phospholipid turnover in response to TRH occurred in 6. Neither of the 2 prolactinomas exposed to GnRH responded to GnRH, whereas all 5 prolactinomas responded to TRH. These findings demonstrate the presence of functional GnRH receptors on endocrinologically inactive pituitary adenomas. The phosphatidyl inositol-linked receptor status of these tumors differs from that of prolactinomas. These receptors may offer a possible target for therapeutic intervention in endocrinologically inactive adenomas.