progesteronu

Progesterone is a steroid hormone of the progestogen class that plays a central role in female reproduction and in the maintenance of early pregnancy. In humans, the primary sources are the corpus luteum of the ovary during the luteal phase of the menstrual cycle and the placenta during pregnancy; small amounts are also produced by the adrenal glands. Progesterone is synthesized from cholesterol through a series of enzymatic steps, with pregnenolone as an intermediate. In pregnancy, placental production increases to support the developing fetus.

Progesterone exerts its effects mainly by binding to intracellular progesterone receptors (PR-A and PR-B). Binding alters gene transcription and modulates cellular functions over hours to days. There are also rapid, non-genomic actions via membrane-associated receptors and other pathways, which can affect uterine contractility, immune responses, and neuronal activity.

In the menstrual cycle, progesterone promotes transformation of the endometrium into a secretory lining that can support implantation after ovulation; it reduces uterine contractions and modulates cervical mucus. During pregnancy, it helps maintain the uterine environment, supports placental function, and contributes to immune tolerance of the fetus. Progesterone also influences mammary gland development in preparation for lactation and has various effects on other tissues including the brain and bone.

Medically, progesterone or progestogens are used to support luteal phase in assisted reproduction, to treat progesterone deficiency, and as part of menopausal hormone therapy to protect the endometrium when estrogen is given. Vaginal or oral formulations are used for different indications, including prevention of preterm birth in high-risk pregnancies when indicated.

Progesterone biosynthesis is regulated by gonadotropins, particularly luteinizing hormone, and by ovarian and placental function. It is metabolized in the liver to several metabolites, such as pregnanediol, and is excreted in urine. The half-life in circulation is relatively short, but effects persist through receptor-activated gene regulation.