Estrogens are present in significant amounts in both men and women. They are present in significantly higher amounts in women after menarche (onset of menstrual periods at puberty) until menopause (cessation of menstrual periods after completion of reproductive age).
The primary function of estrogens is development of female secondary sexual characteristics. These includes breasts, endometrium, regulation of the menstrual cycle etc. In males estrogen helps in maturation of the sperm and maintenance of a healthy libido.
Physical functions
Estrogen is responsible for development of the female body and the secondary sexual characters. It helps decelerate height increase in females during puberty, accelerates burning of body fat and reduces muscle bulk.
It also stimulates growth of the inner lining of the uterus (endometrium) during the menstrual cycle, increases uterine growth, improves lubrication of the vagina, and thickens the vaginal wall while increasing blood vessels to the skin.
Effects on various biochemical parameters
Estrogens reduce bone resorption and increase bone formation.
They help in protein synthesis, increase hepatic production of binding proteins, coagulation proteins (factors II, VII, IX, X, plasminogen). Estrogens increase platelet adhesiveness and reduce antithrombin III.
Estrogens increase good cholesterol (HDL) and also increase triglycerides. They decrease LDL and promote fat deposition.
On fluids and electrolytes estrogens cause salt (sodium) and water retention. In the gastrointestinal tract they reduce bowel motility and increase cholesterol in bile. They also improve lung functions.
Effects on hormones
Estrogens increase cortisol and Sex hormone binding globulin. Estrogens increase melanin and pheomelanin and reduce eumelanin.
Estrogens and cancer
Estrogens help in the growth and maintenance of hormone-sensitive breast cancers.
Estrogen and libido
Sexual desire is dependent on androgen levels rather than estrogen levels
Estrogen and development of the fetus
Estrogen helps in causing physical differentiation of the fetus to either males or females as per their genetic code. While androgens like testosterone lead to masculinizing the fetus, estrogen feminizes the fetus. Prenatal androgens act on behavior and other tissues, with the possible exception of effects on bone via androgen receptors.
Estrogen and mental health
Estrogen is considered to play a significant role in women’s mental health. Sudden decrease in blood levels of estrogen and periods of sustained estrogen low levels correlate with significant mood lowering.
After childbirth, nearing menopause and after menopause low levels of estrogen can predispose to depression.
Estrogen and skin
For many years it has been recognized that estrogens are important in the maintenance of human skin. They improve collagen content and quality, increase skin thickness and improve blood supply to the skin. Estrogens act via estrogen receptors on human skin.
The number of estrogen receptors varies in different parts of the body. Highest receptor levels are seen on the facial skin and skin over thigh or breast.
Estrogen and heart disease
Estrogen deficiency increases the risk of heart disease. Lack of estrogen is an impetus to atherosclerosis.
Estrogen in men
Males also possess estrogen receptors and estrogen to some extent and levels in the male blood are higher than post-menopausal women. Estradiol has been found to be responsible for initiating spermatogenesis or formation and maturation of sperms in men. It helps in bone strength, sexual maturation and cholesterol metabolism.
Further Reading
Postmenopausal hormone therapy use declines amidst risk-benefit concerns