Every estrogen in your body starts life as an androgen like testosterone
The so-called female hormone is built from male ones. An enzyme called aromatase converts testosterone and androstenedione into estrogens, and in both sexes androgens actually circulate at higher levels. Men need estrogen too, for sperm maturation and probably libido, and one study found fathers carry more estradiol than men without children.
Estrogens are a family of steroid sex hormones made by all vertebrates and even some insects. The main ones are estrone, estradiol and estriol, with a fourth, estetrol, appearing only in pregnancy. Which dominates depends on life stage. Estradiol is the most potent and prevails from puberty to menopause; in mouse tests it is roughly ten times stronger than estrone and a hundred times stronger than estriol. Estriol takes the lead during pregnancy, and estrone after menopause.
Being steroids, estrogens slip straight through cell membranes. Inside, they bind estrogen receptors, proteins that attach to specific DNA sequences and switch target genes on; one study in a breast cancer cell line identified 89 such genes. Because the hormone enters every cell, its effects depend on which tissues carry receptors, notably the ovary, uterus and breast. A separate family of membrane receptors handles faster signalling.
In puberty, estrogens drive breast development, wider hips and a fat pattern favouring the breasts, buttocks and legs over the abdomen. A surge of estrogen triggers the release of luteinising hormone, which prompts ovulation, and together with progesterone it prepares and maintains the uterine lining. Androgens such as testosterone oppose estrogen's action in breast tissue. Estrogens also influence metabolism, and deficiencies are linked to obesity.
The brain responds too. Verbal memory scores track estrogen levels across the menstrual cycle, pregnancy and menopause, though effects on cognition vary with timing and task. Sudden drops or prolonged low levels correlate with lowered mood. Estrogens are used medically in menopausal hormone therapy and hormonal contraception, but synthetic and natural estrogens that escape into the environment act as endocrine disruptors, harming reproduction in wildlife and people.
Source: Estrogen
