Response of the Hypothalamic-Pituitary-Testicular Axis to Surgery

Abstract

To evaluate the response of the hypothalamic-pituitary-testicular axis to surgery, serum levels of gonadotropins and steroid hormones were measured prior to and after elective surgery in men under age 50. Twelve men having surgery under general anesthesia had significant decreases in serum testosterone levels after surgery (P < 0.02). Six men having surgery under spinal or local anesthesia did not show a significant reduction in serum testosterone. By the 2nd postoperative day, the magnitude of the decreases in serum testosterone and serum free testosterone were similar (23% and 25%, respectively) in men having surgery under general anesthesia, and the changes in serum testosterone and serum free testosterone were significantly correlated (r = 0.69, P < 0.02). In subjects having general anesthesia, serum levels of estradiol, androstenedione, and 17-hydroxyprogesterone tended to fall, although not significantly, while serum follicle-stimulating hormone and the testosterone to estradiol ratio did not change. Serum luteinizing hormone (LH) levels increased by a mean of 19% after surgery under general anesthesia, although this increase was not statistically significant. The concomitant fall of serum testosterone and serum free testosterone after surgery under general anesthesia suggested that this fall is due to a decrease in testosterone secretion rather than a primary change in testosterone clearance or serum binding of testosterone. This decrease in testosterone secretion was not due to a specific block in the distal steps of testosterone biosynthesis nor to hypothalamic-pituitary suppression by elevated estradiol levels. The nonsignificant increase in serum LH is consistent with either a primary testicular defect or hypothalamic-pituitary dysfunction as the cause of the fall in serum testosterone after surgery under general anesthesia.