Molecular mechanism of progesterone action in the female reproductive system

Progesterone (P4) is a steroid hormone which participate in many processes in the female reproductive system. The hormone is produced mainly by the corpus luteum (CL), however, also the ovarian follicles, uterine tissues and placenta are able to produce P4. Progesterone is involved in the regulation of the sexual cycle, as well as in the initiation and maintenance of pregnancy. The hormone may affect cell function by genomic mechanism, through nuclear P4 receptors (PGR), and via nongenomic mechanism, through the membrane P4 receptors, such as progesterone receptor membrane component (PGRMC) 1 and 2, and membrane progestin receptors (mPR) α, β and γ. The genomic mechanism of P4 action leads to the expression of target genes and the synthesis of new proteins, while the nongenomic mechanism modifies various intracellular signaling pathways. The integration of these two mechanisms of P4 activity leads to the suitable regulation of the cell, tissue and, consequently, the response of organism to the hormone.