Effect of synthetic ovine corticotropin-releasing factor on growth hormone secretion in patients with acromegaly.

Abstract

In a significant proportion of patients with acromegaly, a non-specific increase in plasma growth hormone (GH) has been recognized following administration of thyrotropin-releasing hormone (TRH) or luteinizing hormone-releasing hormone (LH-RH), probably due to the lack of the specificity of the receptor in their tumor cells. In this study, the effects of corticotropin-releasing factor (CRF), a newly isolated hypothalamic hormone, in addition to TRH and LH-RH, on plasma levels of GH and the other anterior pituitary hormones were evaluated in 6 patients with acromegaly. Synthetic ovine CRF (1.0 microgram/kg), TRH (500 micrograms) or LH-RH (100 micrograms) was given as an iv bolus injection, in the morning after an overnight fast. Blood specimens were taken before and after injection at intervals up to 120 min, and plasma GH, adrenocorticotropin (ACTH), thyrotropin, prolactin, luteinizing hormone, follicle-stimulating hormone and cortisol were assayed by radioimmunoassays. A non-specific rise in plasma GH was demonstrated following injection of TRH and LH-RH, in 5 of 6 and 2 of 5 patients, respectively. In all subjects, rapid rises were observed in both plasma ACTH (34.3 +/- 6.2 pg/ml at 0 min to 79.5 +/- 9.5 pg/ml at 30 min, mean +/- SEM) and cortisol level (9.1 +/- 1.3 micrograms/dl at 0 min to 23.4 +/- 1.2 micrograms/dl at 90 min). However, plasma levels of GH and the other anterior pituitary hormones did not change significantly after CRF injection. These results indicate that CRF specifically stimulates ACTH secretion and any non-specific response of GH to CRF appears to be an infrequent phenomenon in this disorder.