Pharmacokinetics of progesterone concentrations was around 4 hours and the elimination half-life was in the range of 30 to 40 hours. The venous blood levels observed were very low. Because progesterone is a lipophilic and hydrophobic compound, it is not absorbed efficiently by the skin. Moreover, because the body produces about 25 mg progesterone per day on average during the luteal phase, around 50% of the body would need to be used as a surface of absorption to deliver a similar quantity of progesterone. As such, the transdermal route cannot easily achieve adequate circulating progesterone levels, and this makes transdermal progesterone impractical for
Menstrual synchrony one menstrual onset for each woman in a couple, they calculated the degree of synchrony. They reported that more than half of the couples had synchronized within a two-day timespan of each other. Trevathan, Burleson, and Gregory also conducted a study with 29 lesbian couples (22 to 48 years of age), but they incorporated the methodological critique of Wilson into the design of their study. In particular, Wilson emphasized the importance of using actual menstrual cycle lengths with their inherent variability. The lesbian couples were drawn from a larger sample of women who had kept daily records of their menstrual