Estrogen

Estrogen is a hormone, made mostly by the ovaries until menopause. The British Menopause Society says it does far more than run the menstrual cycle: during the reproductive years it plays an important part in keeping bones and heart healthy, and in how the brain works.

It is really a family of hormones. Women's Health Concern lists four that occur naturally:

• estradiol, the strongest, made mainly by the ovaries before menopause, and the one most HRT contains
• estrone, a weaker kind, which becomes the main estrogen after menopause and is made in fatty tissue
• estriol, made by the placenta in pregnancy
• estetrol, made only by an unborn baby's liver

The estrogen a lab measures in a blood test is estradiol.

In perimenopause, Women's Health Concern says, estrogen moves far less predictably than across an ordinary monthly cycle. It can climb above the usual range and drop below it.

Each direction has its own feel. When estrogen is low, it says, you may get hot flushes or night sweats. When it is high, you may get breast tenderness or headaches. And the change itself can trigger low mood, anxiety or migraine in some women. So you can feel fine for a fortnight and then not, with no change in your life to explain it.

Women's Health Concern explains it simply: during your fertile years your ovaries make estrogen, and as you get older your store of eggs falls and estrogen drops with it. It does not happen overnight. The process takes several years, which is why symptoms can come and go.

After menopause, it says, the body generally adapts to lower estrogen, and symptoms usually start to settle once periods stop, though they can carry on for an unpredictable number of years.

The British Menopause Society names two long-term effects of lower estrogen. The first is on bones: a woman's skeleton depends on estrogen for its strength, and the loss raises the risk of osteoporosis, which often has no symptoms until a bone breaks. The second is on the heart: it says estrogen deficiency after menopause has been shown to raise the risk of heart disease.

Women's Health Concern says the same. For South Asian women there is one more reason to watch the heart: the British Menopause Society notes a higher rate of heart risk factors, such as insulin resistance, diabetes and high blood pressure, during the transition.

The Pakistan Menopause Society adds a useful balance. It asks doctors not to imply that every midlife illness comes from low estrogen alone, because age, lifestyle and other conditions also play a part (Table 1).

The British Menopause Society calls estrogen the main part of HRT. It can be taken as a tablet or through the skin, as a patch, gel or spray. See estrogen gel and estrogen patches.

Women who still have a womb are also given a progestogen, such as progesterone, to protect its lining from the effects of estrogen. The Pakistan Menopause Society and the British Menopause Society both say estrogen on its own is for women who have had a hysterectomy (PMS section 5.4).

Estrogen can also be used just in the vagina, which the Pakistan Menopause Society lists for genitourinary symptoms such as dryness (section 5.4). See vaginal estrogen.

Whether any of these suits you depends on your age, your health and your family history, and that is your doctor's decision to make with you.

If symptoms are getting in the way of your sleep, work or home life, see a doctor. You do not need a blood test first: Women's Health Concern says an estrogen test is rarely useful in perimenopause, because the level can vary so much from person to person and hour by hour. More in Is there a test for menopause?

Any bleeding after your periods have stopped for a year needs checking, whatever you think is behind it. The Pakistan Menopause Society lists it as a red flag (section 2.3).