In order to understand how menopause occurs it is important to have a basic understanding of the normal female physiology during reproductive years.
During menstruation, low levels of oestrogen and progesterone are released into the bloodstream. The hypothalamus controls the secretions of these hormones through the release of luteinizing hormone releasing hormone (LHRH), which then stimulates the pituitary gland to produce follicle stimulating hormone (FSH). FSH, in turn, stimulates the ovaries to produce oestradiol, which causes the endometrium to proliferate. As circulating levels of oestradiol increase, FSH and luteinizing hormone (LH) levels fall until around day 14 of the cycle. LH concentration then peaks and ovulation generally occurs. If fertilization does not take place, oestrogen and progesterone levels fall and the endometrium is shed – menstruation takes place. The falling levels of oestrogen and progesterone are detected by the hypothalamus and the cycle starts again.
From around the age of 35 years, the natural cycle becomes less predictable and ovulation may not occur in every cycle. Oestrogen levels fall and, as a result of the negative feedback system of the pituitary and hypothalamus glands, more and more FSH is released in an attempt to stimulate ovarian function. When oestrogen levels fall too low to stimulate endometrial growth, bleeding stops altogether and the menopause occurs.
Follicle stimulating hormone
Hormonal changes begin well before a woman sees an alteration in her menstrual pattern. Fluctuations in the levels of FSH and LH occur throughout the perimenopause, eventually peaking 2-3 years after periods stop and remaining high for the next 20 years or so, unless hormone replacement therapy (HRT) is taken (Teede & Burger 1998). FSH levels fluctuate widely during the menopausal transition.
Oestradiol and oestrone
In the premenopausal woman, both oestradiol and oestrone are present, with oestradiol being the dominant hormone. Both are secreted by the ovaries but oestrone is also available through conversion in fatty tissue of the hormone androstenedione, which is secreted by the adrenal glands. Oestrone is biologically less active than oestradiol. After the menopause, the ratio of oestradiol to oestrone changes, with oestrone becoming the dominant hormone. There may be transient periods of excess oestrogen, even with raised FSH levels (Teede & Burger 1998).
Many women believe that they need a blood test to confirm whether or not they are menopausal. In practice such tests are often unnecessary. Symptoms of the menopause do not correlate with actual levels of circulating oestrogen. Some women experience symptoms whilst maintaining relatively high oestrogen levels, whereas others, even with lower levels, may not have such bad symptoms.
Measurement of FSH levels will help diagnose the menopause, but as levels fluctuate widely in the perimenopause repeated determination of the level would be required to be certain of an accurate result. Measuring FSH or oestradiol concentration will not help in predicting whether or not a woman needs HRT. However, FSH levels may be useful in the following circumstances:
- Hysterectomized women
- Diagnosis of premature menopause, which may have medical or psychological implications
- To confirm lack of ovarian function for women seeking advice about contraception
Effect of hysterectomy on menopause
It is possible that, even if the ovaries are conserved at the time of hysterectomy, vascular supply to the ovaries may be compromised, resulting in the menopause occurring earlier than it otherwise would. If a woman experiences an hysterectomy, but is asymptomatic, of osteoporosis and cardiovascular is not detected.
Women approaching the menopause can now expect to live for many more years; many women are living into their eighties and beyond. It is therefore becoming increasingly important to women that the postmenopausal years are as healthy as those before the menopause. Women often ask, ‘Why must I think about the menopause, when my grandmother just got on with it ? The truth is that far fewer women of her grandmother’s generation lived for many years after the menopause. It is not the menopause that has changed in character (although we do have a greater understanding of the physical changes now), but rather that women’s expectation of life beyond the menopause has changed.
The menopause is a natural event which marks the end of fertility and the end of periods. The menopause itself is merely the outward manifestation of all the hormonal changes that will occur in a woman at this time. Helping women to understand the physiological causes of menopause and reminding them how their bodies normally function is the first step in helping them to come to terms with their changing body and then with all the other changes that may be occurring at the same time.
1) Cramer DW, Xu H, Harlow BL (1995) Family history as a predictor of early menopause.
2) McKinlay SM, Bifano NL, McKinlay JB (1985) Smoking and age at menopause in women.
3) Sharara FI, Beatse SN, Leonard MR et al (1994) Cigarettes smoking accelerates the development of diminished ovarian reserve as evidenced by the clomiphene citrate challenge test.
4) Siddle N, Sorrel P, Whitehead MI (1987) The effect of hysterectomy on the age of ovarian failure: identification of a subgroup of women with premature loss of ovarian function.