Oestradiol

Oestradiol is the main oestrogen, the hormone that carries the first half of the cycle in women. It is made in the ovaries, in the maturing follicle, and in the weeks after menstruation it builds up the lining of the womb, makes the mucus around ovulation permeable and, once it is high enough, gives the brain the signal for the LH surge that sets ovulation in motion. After ovulation it falls back and progesterone takes over. It does more than the cycle. Oestradiol keeps bone strong, keeps the artery wall supple, helps cholesterol the right way and acts on skin, sleep and mood. That is why the years after the menopause, when it falls away, bring osteoporosis and cardiovascular disease closer. And it is present in men too: a small part of testosterone is converted into oestradiol in fat tissue and bone, and that small part keeps bone intact in men as well. Your report shows oestradiol in pmol/L, and in women not with one range but with a range per phase of the cycle: low at the start, a peak around ovulation, an intermediate level in the second half and a low value after the menopause. Those phases differ by multiples, not margins, so without a cycle day the number cannot be read. In men there is one range, about 40 to 162 pmol/L at most labs.

For anyone who wants to stay healthy, oestradiol is above all a signal that your cycle is doing what it should. A regular cycle with ovulation is one of the most reliable signs that your body has enough energy, rest and fat, and it is one of the first things to switch off when it does not. Eating too little for what you burn, training a lot, losing weight fast or lasting stress turn the signal from the brain down low, and oestradiol falls with it. Missed periods in a sporty, lean woman are then not fitness but a deficit, and bone pays the price. The second reason is the menopause. In the years before it oestradiol starts to fluctuate, high and low by turns, while FSH climbs; afterwards it stays low. That explains hot flushes, worse sleep, dry mucous membranes and the faster bone loss of those years. An oestradiol value shows that, but one measurement says little in a phase that fluctuates by definition: symptoms and the absence of periods say more, and the menopause is not diagnosed on the number. In men oestradiol is the value that gives away belly fat. Fat tissue converts testosterone into oestradiol, so the more belly fat, the higher the oestradiol and the lower the testosterone: the pattern behind breast tissue, less desire and less muscle in men with excess weight. Too low rarely happens by itself in men; it goes with drugs that block the conversion, and then bone suffers. Anyone using hormone therapy or contraception measures something else. The pill suppresses production of your own, and hormone therapy after the menopause supplies oestradiol from outside; the number then says something about the dose, not about your ovaries.

A high oestradiol in women is almost always a matter of timing: around ovulation the value belongs a multiple higher than at the start of the cycle, and setting a value from those days against the range of the first half turns a normal peak into an abnormality. In pregnancy oestradiol climbs to a multiple of any cycle value. In men high is usually belly fat, and sometimes testosterone from outside, because that too is partly converted. A low oestradiol is the ordinary picture at the start of the cycle and after the menopause. Beyond those the question is what it comes from. In a woman of reproductive age with a missing cycle, a low oestradiol together with a low FSH and LH points at the signal from the brain, and that is usually an energy deficit, overtraining, fast weight loss or stress; together with a high FSH it points at ovaries responding less, as in the years before the menopause. The pill also gives a low oestradiol of your own, and that is then the intention. The levers are those of your energy balance and your fat mass. With a cycle that switches off from eating too little or training too much, oestradiol recovers once the balance returns: more food, especially carbohydrates and fat, fewer training hours, more sleep; that usually takes months, not weeks. In men with a high oestradiol and a low testosterone, losing weight around the middle works both ways: less conversion and more testosterone of your own. After the menopause the lever is not the hormone itself but bone and heart: strength training, calcium and vitamin D, and the ordinary lifestyle for your vessels. Hormone therapy is there for anyone with many symptoms, and that is a choice you make together with a doctor. Never read oestradiol on its own. FSH and LH tell you how hard the brain is pulling on the ovaries, progesterone whether ovulation has happened, and in men testosterone belongs beside it. Note your cycle day, and whether you use contraception or hormones, because without that context the number cannot be placed.