Effect of oral contraceptives on adrenocorticotropin and growth hormone secretion following CRH and GHRH administration

Previous investigations have demonstrated that basal ACTH plasma levels are reduced and that GH levels are either increased or unchanged in women taking oral contraceptives. The purpose of the present investigation was to determine the secretion of ACTH and GH following an intravenous infusion of human corticotropin releasing hormone (CRH) and human growth hormone releasing hormone (GHRH) in control women (N = 8) and in women taking a triphasic oral contraceptive (N = 9). The studies were initiated between 7:00 and 9:00 a.m. and all women were fasting. An intravenous catheter attached to a 3-way stopcock was used for blood sampling and to inject a bolus of CRH and GHRH ( 1μg kg). Plasma samples were frozen immediately and stored at -70 °C until assayed for content of ACTH and GH by radioimmunoassay. The plasma levels of ACTH and GH increased following infusion of CRH and GHRH in all women. The mean plasma levels of growth hormone were not statistically different in oral contraceptive users compared to normal women. In contrast, ACTH plasma levels in oral contraceptive users were reduced approximately 25% overall, and significantly lower (p<0.04) at 120 minutes following the CRH infusion compared to controls. In conclusion, the GHRH-stimulated GH release was similar in normal women and oral contraceptive users. CRH-stimulated ACTH release was modestly reduced in oral contraceptive users compared to normal women suggesting that estrogens and progestogens may have a suppressive effect on the release of ACTH by the pituitary.