Pituitary-Adrenal Dynamics During Surgical Stress

Publisher Website
Google Scholar
Abstract
Under nonstressful conditions, the pituitary-adrenocortical system appears to be regulated, at least in part, by a negative feedback mechanism whereby an increase in plasma cortisol suppresses corticotropin (ACTH) secretion while a decrease in plasma cortisol leads to an increase in the secretion of ACTH. In response to certain stresses, however, both ACTH and cortisol are secreted in increased quantities. The present study was designed to determine what role, if any, the negative feedback mechanism plays in regulating ACTH secretion during the acute stress of pelvic laparotomy. As compared with preoperative levels, plasma 17-hydroxycorticoids (17-OHCS) increased by 17–36 μg/100 ml and urinary 17-OHCS increased by 4–20 mg/day in 22 patients undergoing pelvic laparotomy without exogenous steroids. Similar increases in 17-OHCS were observed in 10 patients given 8 mg of dexamethasone phosphate intramuscularly before the operation and in 7 patients given dexamethasone phosphate intravenously at the rate of 5 or 10 mg/hr throughout the operation. To make possible the assessment of adrenal secretion during treatment with massive doses of exogenous cortisol, 4 patients were given infusions of Metopirone (Su-4885) during operation, and endogenous adrenal activity was followed by specific measurement of substance S in plasma and tetrahydro S in urine; the pituitaryadrenal response to laparotomy was not suppressed by infusions of cortisol which maintained plasma cortisol levels between 100 and 500 μg/100 ml. The concentration of ACTH in plasma obtained during laparotomy from 9 patients receiving exogenous cortisol was not significantly different from that of 13 control patients undergoing laparotomy without exogenous steroids. It is concluded that during the stress of laparotomy the behavior of the human pituitary-adrenal system does not conform to the specifications of a negative feedback mechanism.