Oestrogen deficiency as the cause of most menopausal symptoms
Most menopausal symptoms come from falling ovarian oestrogen once the follicles (the fluid-filled sacs in the ovary that each hold an egg and make oestrogen) run out.
Remember
Falling ovarian oestrogen, after the follicles have run out, causes most menopausal symptoms. The rise in FSH and LH (hormones from the pituitary gland that stimulate the ovaries) is a response, not the cause.
Memory aid
the ovaries stop answering, the pituitary shouts louder, and what the woman feels is the missing oestrogen
It separates the cause of the symptoms, the missing oestrogen, from the pituitary gland's response, the raised FSH and LH.
The natural menopause happens when the ovaries run out of follicles. With so few left, the ovaries can no longer make enough oestrogen to keep ovulation and periods going.
Oestrogen acts on many tissues, so its loss shows up in several places. Hot flushes and night sweats are called vasomotor symptoms, because the body's control of its blood vessels and sweating becomes unstable. They are thought to arise from changes in the hypothalamus, which acts as the body's thermostat. Vaginal dryness and urinary symptoms follow the same oestrogen loss, and thinning of the bones comes later.
The pituitary gland reacts to the failing ovaries. Oestrogen and inhibin (another hormone made by follicles) normally hold the pituitary gland back, a brake called negative feedback. When both fall, the brake is released and the pituitary gland releases more FSH and LH. The ovaries respond poorly, so the pituitary gland produces more and more of them. A high FSH can suggest that the menopause has begun, although it is not always reliable.
That rise is a result of ovarian failure, not the cause of the symptoms. This is why most of the symptoms are due to oestrogen deficiency rather than to the raised FSH and LH.
Key facts
- Cause
- the ovaries run out of follicles, so ovarian oestrogen and inhibin fall.
- Symptoms
- most come from low oestrogen, including hot flushes, night sweats and vaginal dryness, with thinning of the bones later.
- Feedback
- FSH and LH rise because the brake that normally acts on the pituitary gland is lost, so a high FSH is a result and not the cause of the symptoms.
- Hot flushes
- they are thought to arise from changes in the thermoregulatory centre (the body's thermostat) in the hypothalamus, although the exact mechanism is not fully understood.
- Treatment
- HRT (hormone replacement therapy) works by replacing the lost oestrogen.
Exam traps
- Raised LH is tempting because it does rise, but the rise is the pituitary gland reacting to lost ovarian hormones, and the ovaries, which have very few follicles left, respond poorly. Most of the symptoms come from the missing oestrogen.
- Progesterone does fall, because ovulations become less frequent, but the symptoms are attributed mainly to oestrogen deficiency rather than to progesterone.
- FSH does not fall in the menopause, it rises, because oestrogen and inhibin no longer provide negative feedback. A low FSH would point to a pituitary problem rather than to the menopause.
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