Objective: To investigate the relation between gonadal steroids and the 24-hour body temperature rhythm.
Patient(s): Nineteen normally cycling women.
Design: Controlled clinical study in volunteer women.
Setting: Clinical hospital.
Intervention(s): 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.
Main outcome measure(s): 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.
Result(s): 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.
Conclusion(s): 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.