Medroxyprogesterone increases basal temperature: a placebo-controlled crossover trial in postmenopausal women

To assess whether temperature is increased by medroxyprogesterone (MPA) and thus whether basal temperature records could be used to determine ovulation during cyclic MPA therapy.

A 2-month double-blind placebo-controlled crossover trial in which oral basal temperature was measured daily.

Normal human volunteers in an academic medical environment.

Eleven postmenopausal women not taking gonadal hormones.

Medroxyprogesterone acetate (10 mg/d) or placebo, calendar days 16 to 25, with crossover.

Comparison of mean temperature days 17 to 26 during MPA versus placebo; comparison of differences between temperatures days 7 to 16 and 17 to 26 in MPA versus placebo months; and analysis for a significant monthly thermal shift.

The mean temperatures during MPA treatment averaged 0.27 degrees C higher than during the placebo phase and showed a significant change from pretreatment to "treatment" phases during MPA but not during placebo cycles. Eight of the MPA and one of the placebo cycles showed a shift from lower to higher temperatures days 16 to 25.

Medroxyprogesterone acetate has a physiological progesterone-like thermal effect. Therefore basal temperature data cannot reliably indicate ovulation during cyclic MPA administration.