The association between plasma calcitonin and β-endorphin has been shown in various studies with analgesic and thermoregulatory effects. In the present study, we sought a similar association between those chemicals and physiological menopausal hot flush. Plasma calcitonin and β-endorphin levels were measured in 5 women in physiologic menopause who suffered from frequent episodes of hot flushes. An increase in plasma calcitonin levels was noted during the hot flushes, although it was not significant. In contrast, plasma β-endorphin levels fell significantly at onset of the hot flush, as compared to their levels 5–20 min earlier (p < 0.005), and rose 5–15 min following the hot flush e