Menstrual cycle mating partners during the menstrual cycle; however, those seeking a short-term relationship were more likely to choose a partner with more masculine features than usual. This was found to be the case especially during the woman's high conception risk stage and when salivary testosterone was high. However, when women are in the luteal (non-fertile) phase, they tend to prefer men (and females) with more feminine faces. A preference is also shown for self-resembling faces and apparent health in faces during the luteal phase of the cycle. Apparent health preferences were found to be strongest when progesterone levels were high. Additionally,
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