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.