Pharmacodynamics of progesterone women, this effect being the result of suppression of the mid-cycle surge in gonadotropin secretion, is 300 mg/day. However, this figure is based on limited clinical data. Conversely, treatment with a high dosage of oral progesterone of 100 mg four times per day (or 400 mg/day total) in men for 10 days that resulted in approximately mid-luteal phase levels of progesterone (7.9–9.4 ng/mL; measured by ) did not cause any change in testosterone levels, suggesting that progesterone has little or no antigonadotropic effect in males at typical clinical dosages. In addition, a study found that administration of 1,000 mg/day oral
Pharmacokinetics of progesterone half-life of progesterone in the circulation is very short at a range of about 3 to 90 minutes. Previous studies using RIA have reported an overestimated half-life of oral progesterone of about 16 to 18 hours. A subsequent, reliable study using high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS) reported a half-life of oral progesterone of about 4.6 to 5.2 hours when it was taken with food. Due to the short half-life and duration of action of oral progesterone, it is often taken in divided doses of two or three times per day. Because of studies that used RIA, it was incorrectly