Menopausal syndrome: plasma levels of beta-endorphin in post-menopausal women measured by a specific radioimmunoassay.

beta-Endorphin (beta-EP) levels were measured in 13 post-menopausal women (7 surgical, 6 physiological) using a new highly specific and accurate radioimmunoassay, and were found to be significantly lower than among 10 normally menstruating controls (48.6 +/- 13.8 pg/ml vs. 70.0 +/- 18 pg/ml, P less than 0.005). beta-EP levels were measured prior to and 5 days after surgery in 3 of the oophorectomized women, and were found to have decreased by an average of 41%. beta-EP levels were measured immediately after hot flashes experienced by 4 of the post-menopausal women during regular clinic visits, and were found to be significantly elevated above baseline levels (P less than 0.02). Our data confirmed the findings of Genazzani et al. [10], a significant lowering of beta-EP at menopause. Also, the data from the small number of beta-EP plasma levels we studied during hot flashes, suggests a possible role of beta-EP either directly or indirectly on the genesis of hot flashes.