Constancy of opioid control of luteinizing hormone in different pathophysiological states

This study assessed the effect of the opiate antagonist naloxone on anterior pituitary hormone release in normal subjects and patients with disturbances of the gonadotropic axis. Intravenous bolus injections of naloxone resulted in a rise of plasma LH, but had no significant effect on plasma levels of FSH or PRL. It also failed to alter the LH, FSH, or TSH response to LRF and TRH, although it did augment the PRL response to TRH. Slow iv infusion of naloxone resulted in increased plasma LH and FSH concentrations in both normal subjects and patients with hyperprolactinemia. The rise of LH correlated with the mean basal LH concentrations; a low basal level only responded to naloxone with a small increase in circulating LH concentration and vice versa. This relationship of the response of LH to the resting levels also held in several other pathological states in which there were marked differences of androgen and estrogen status as well as up to a 100-fold variation in basal LH concentrations. It is concluded that LH is under inhibitory opioid control both in normal subjects and in widely differing pathological states of the gonadotropic axis.