Human Prolactin and Growth Hormone Release during Surgery and other Conditions of Stress1

Abstract

Human plasma prolactin, measured by a homologous radioimmunoassay, has been found to rise significantly in a number of situations associated with stress. The greatest elevations, averaging approximately five-fold, were seen during major surgery with general anesthesia. Absolute levels of prolactin were higher at all times during surgery in women than in men. Smaller but significant elevations were found with gastroscopy, proctoscopy, and exercise. In all situations except exercise the prolactin rise was as high as, or higher than, that of growth hormone. Hypoglycemia induced by 0.2 U/kg of insulin produced significant prolactin elevations in all of seven normal women. Major elevations of prolactin, but not growth hormone, occurred in a minority of normal women following sexual intercourse; prolactin did not rise significantly in their male partners. It is concluded that prolactin in human beings is at least as responsive as growth hormone to release by stress in most situations; the two hormones differ significantly, however, in their response to other stimuli. The release of prolactin in some women following sexual intercourse may be related to stimuli, as yet undefined, other than those associated with stress.