Effect of Progesterone on Testosterone Concentrations and Breast Development in Transwomen

* Purpose. The purpose of this research is study the effect of progesterone therapy on testosterone levels in transwomen who are currently on gender affirming treatment with estradiol. * Duration. It is expected that participation will last for 6 months (24 weeks). * Study Procedures. Participants will be asked to sign an informed consent, complete a medical history, have a physical exam conducted, have a fasting blood sample taken and asked to take a study drug once daily. * Risks. Some of the foreseeable risks or discomforts include temporary discomfort, bleeding, bruising and/or swelling in the arm from blood draw. There are no known direct risks with the use of Progesterone in Transwomen for gender affirming therapy. * Benefits. Some of the possible benefits that may be expected include increase in fat mass, increase in breast size/fullness, decrease in masculine hair patterns.