Bio-identical progesterone is known as a medication with very variable results as part of feminisation hormone therapy. This article tries to explain why that is the case.
Progesterone has a wide range of effects via progesterone receptors, pregnane X receptors, GABA receptor modulation, nicotinic acetylcholine receptor modulation, glucocorticoid receptors, and mineralocorticoid receptors, either directly or via metabolites. This includes actions on water and electrolyte balance, tissue growth, immune function, neurotransmitter levels and modulating effects, and more.
When talking about progesterone with respect to transition there are two main areas which people focus on:
Breast development is a process that takes years, longitudinal studies that follow people through years are expensive and difficult to run and so studies into breast development in trans women are lacking. At best they only cover a year or two which is not enough to track effects. Instead, data from other studies is often extrapolated to infer how hormones may impact feminisation.
Because of the lack of strong evidence for trans healthcare in trans studies, doctors are often hesitant to