Progesterone has a variety of important functions in the body. It helps balance the effects of estrogen, especially in the lining of your uterus. Progesterone is mainly produced by a specific part of your ovary called the corpus luteum. The corpus luteum develops from the follicle that releases an egg at ovulation. After ovulation, the corpus luteum ramps up its progesterone production. Progesterone is the dominant hormone in the second half or luteal phase of your menstrual cycle, and its role is to continue the work of estrogen in preparing the lining of your uterus for pregnancy. If you do not become pregnant, then your corpus luteum dissolves, your progesterone levels drop, and a new menstrual cycle begins.
Progesterone interacts with the chemicals in your brain to control your mood and your general sense of well-being. Progesterone does this via its metabolite, a compound known as allopregnanolone. Allopregnanolone works on a receptor in your brain called the GABA receptor. This is the same receptor that alcohol and the class of medications called benzodiazepines work. Activation of GABA receptors causes a sedative effect. Progesterone enhances the function of serotonin receptors in the brain. Serotonin in the brain helps regulate anxiety, happiness, and mood.
During implantation and gestation, progesterone appears to decrease the maternal immune response to allow for the acceptance of the pregnancy. It is thought that progesterone has anti-inflammatory activity and influence over your immune system; decreasing auto-immune disease flares. It has been postulated, this is the reason why autoimmune flares decrease in pregnancy when progesterone levels are at their highest.
Progesterone potently reduces the sodium-retaining activity of aldosterone, resulting in natriuresis (urination) and a reduction in extracellular fluid volume (edema), that can sometimes arise when there is an imbalance between estrogen and progesterone.
Progesterone, like pregnenolone and dehydroepiandrosterone (DHEA), belongs to an important group of endogenous steroids called neurosteroids. It can be metabolized within all parts of the central nervous system. Previous studies have shown that progesterone supports the normal development of neurons in the brain and that the hormone has a protective effect on damaged brain tissue. It has been observed in animal models that females have reduced susceptibility to traumatic brain injury and this protective effect has been hypothesized to be caused by increased circulating levels of estrogen and progesterone in females.
Progesterone plays a big role in the development of your breasts. Beginning at puberty, progesterone stimulates the growth of breast tissue. The cyclical increase in progesterone concentration and activity in the luteal phase of your menstrual cycle is thought to be the cause of the breast swelling, pain, and tenderness that often occurs in the luteal phase of your menstrual cycle.
Additional functions of progesterone in the body, it decreases contractility of uterus, increases body temperature after ovulation, it’s a natural antidepressant, it normalizes blood clotting, increases zinc and copper levels, helps with new bone growth, and thyroid function, protect against female cancers and increases the body's utilization of fat. Progesterone is also the first hormone to drop as we age, normally becoming significant during the perimenopausal stage of life.