Regulation of the 24-hour rhythm of body temperature in menstrual cycles with spontaneous and gonadotropin-induced ovulation.

To investigate the relation between gonadal steroids and the 24-hour body temperature rhythm.Nineteen normally cycling women.Controlled clinical study in volunteer women.Clinical hospital.Eleven women were studied in the early follicular and luteal menstrual phases of cycles with spontaneous ovulation, and 8 women were studied in the early follicular, preovulatory, and luteal phases of cycles with multiple follicular development.Starting at 5:00 P.M., intravaginal body temperature was monitored continuously for 24 hours and its values were related to E2 and P levels.Twenty-four-hour body temperature rhythm parameters were related to the P:E2 ratio. Very low P:E2 ratios in the preovulatory phase were associated with a reduced 24-hour mean and an elevated body temperature rhythm amplitude. The progressive increase in the P:E2 ratio in the early follicular and luteal phases was associated with an increase in the 24-hour mean body temperature and a decrease in the rhythm amplitude. Body temperature differences between the luteal and early follicular phases were less pronounced in cycles with multiple follicular development.A woman's body temperature is related to her P:E2 ratio. Even in the presence of elevated P values, alterations of this ratio may influence negatively the postovulatory rise in body temperature.