Progesterone is a secondary sex hormone present in natal women that plays a major role in menstrual cycles and pregnancy. Due to it's relationship to certain aspects of breast development there is broad belief within the trans community that Progesterone either helps breast growth or is necessary to complete tanner 4 and 5 stages. While there is currently no hard data supporting its efficacy on those fronts there are several studies [1, 2, 3] showing significiant benefits to mental and emotional function.

While many clinicians treat synthetic Progestins and bioidentical Progesterone as interchangeable based on older care guidelines, more recent studies shows significantly lower risks when using bioidentical Progesterone.

Progesterone is best taken as a rectal suppository to avoid processing in the liver which destroys ~90%. Prolactin levels should be monitored when taking Progesterone.