Oxytocin Does Not Influence Adrenocorticotropin Secretion in Man

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Abstract
Recent studies suggest that oxytocin inhibits ACTH secretion in normal men, whereas previous animal studies indicate that oxytocin is a weak secretagogue of ACTH. We studied the effect of oxytocin on plasma ACTH and cortisol in normal men under three conditions. Using four different doses of oxytocin (30, 60, 90, and 120 mU⁄kg), given by iv bolus injection, we found no difference in the effect of oxytocin on morning ACTH and cortisol levels compared with the effect of a placebo. A prolonged infusion of oxytocin (90 mU⁄kg- h) given from 0300-0600 h did not suppress basal ACTH or cortisol levels or delay or blunt their normal circadian rise. In addition, pretreatment with oxytocin (50 mU⁄ kg, iv bolus dose, followed by an infusion of 50 mU⁄kgh) did not alter the ACTH and cortisol responses to vasopressin. We conclude that oxytocin is not a major regulator of pituitary- adrenal activity in normal men.