Oestrogen- HRT ABC

Oestrogen is the primary female sex hormone. It is responsible for the development and regulation of the female reproductive system. There are three major endogenous (produced by the body) oestrogens in females: estrone, estradiol, and estriol.

The steroid estradiol is the most important. Once inside the cell, estradiol binds to oestrogen receptors (ERs). It acts like a switch, and activates the oestrogens, allowing them to exert their effect on the cells.

The four major naturally occurring oestrogens in women are estrone (E1), estradiol (E2), estriol (E3), and estetrol (E4). Each of these has a slightly different function. Their respective levels will vary depending on where you are within your reproductive life.  

What is the role of Oestrogen in the body?

It is pivotal for many functions of women body. Below are some of the functions.

  • Structural
    • Control the formation of female secondary sex characteristics. Such as breast development, widening of hips and increased fat storage.
    • Accelerate metabolism.
    • Stimulate endometrial (womb lining) growth.
    • Increase uterine growth and thicken the vaginal wall.
    • Vaginal lubrication.
    • Reduce bone resorption (the release of minerals, particularly calcium from the bone). This is important to minimise the risk of osteoporosis.
  • Lipid
    • Increase HDL, triglyceride (the so called “good fats”)
    • Decrease LDL, fat deposition
  • Fluid balance
    • Salt (sodium) and water retention
  • Gastrointestinal tract
    • Reduce bowel motility (beneficial for keeping oestrogen levels constant)
    • Increase cholesterol in bile (important for the absorption of “good fats”)
  • Cancer
    • Support hormone-sensitive breast cancers
  • Uterus lining
    • Oestrogen together with progesterone maintains the uterus lining and uterus function during pregnancy. Also regulates oxytocin receptors in the myometrium (the mechanism for starting contractions during childbirth).
  • Ovulation
    • A surge in oestrogen levels induces the release of luteinizing hormone. Which then triggers ovulation by releasing the egg from the follicle in the ovary.
  • Sexual behaviour
    • Sex drive in both men and women is dependent on androgen levels (a predominantly male hormone) only in the presence of oestrogen. But without oestrogen, the free testosterone level decreases sexual desire.

Once in menopause, your oestrogen levels decrease. Because of this, you may experience all the menopausal symptoms. Restoring oestrogen levels by using HRT can be extremely beneficial.