Oestrogens are renowned as female sex hormones, but they are also produced in small quantities in the male. They are C18 steroids derived from cholesterol via androgen intermediates.
They are synthesised in the:
- ovaries within the:
- theca interna
- granulosa cells
- corpus luteum
- placenta during pregnancy
- adrenal cortex
- Leydig interstitial cells of the testis
The functions of oestrogens are varied; they are commonly associated with feminization and fertility.
The oestrogens produced naturally are 17beta-oestradiol, oestrone and oestriol.
- oestrone (estrone E1)
- formed from oestradiol in a reversible reaction
- predominant form of circulating estrogen after menopause
- oestrone is also a product of the peripheral conversion of androstenedione secreted by the adrenal cortex
- oestradiol-17beta (estradiol E2)
- primarily produced by theca and granulosa cells of the ovary
- predominant form of oestrogen found in premenopausal women
- oestriol (estriol E3)
- oestrogen the placenta secretes during pregnancy
- also is the peripheral metabolite of oestradiol and oestrone
- is not secreted by the ovary
Oestrogen is involved in both female and male reproduction, as well as numerous other biological systems including the neuroendocrine, vascular, skeletal, and immune systems
- also implicated in many different diseases and conditions such as infertility, obesity, osteoporosis, endometriosis, and a variety of cancers
- works through its two distinct nuclear receptors, Estrogen Receptor (ER) alpha and ER beta
- expression profiles of ER alpha and ER beta are unique
- primary sites of ER alpha expression being the uterus and pituitary gland
- main site of ER beta expression being the granulosa cells of the ovary