Progesterone is a naturally occurring steroid hormone essential for regulating the female reproductive system, primarily produced by the ovaries' corpus luteum, placenta during pregnancy, and adrenal glands. It plays a critical role in preparing the uterine lining for pregnancy after ovulation by promoting endometrial thickening and inhibiting uterine contractions to support early gestation. As a potent agonist of nuclear and membrane progesterone receptors, it influences ribosomal transcription, oocyte maturation, sperm motility, and immune modulation while counteracting estrogen effects to prevent endometrial overgrowth. Progesterone also relaxes smooth muscle, reduces inflammation, normalizes blood clotting and vascular tone, and elevates core body temperature during the luteal phase.