LH

LH, luteinising hormone, comes from the same gland as FSH, the pituitary, and acts on the same organs. Where FSH lets the follicles mature, LH gives the starting signal: once the maturing follicle makes enough oestradiol, the pituitary releases a large amount of LH in one go, and about a day later the egg is released. That surge lasts a day or two, and it is that surge an ovulation test picks up in urine. Afterwards LH turns the empty follicle into the corpus luteum, which makes progesterone. In men LH is the hormone that sets the testes to making testosterone. Here too a thermostat is at work: if there is enough testosterone, the pituitary releases less LH; if there is too little, more. That is why, with a low testosterone, LH tells you where the problem sits: a high LH means testes that no longer deliver, a low LH means a brain that is not asking. Your report shows LH in U/l, in women with a range per cycle phase, of which the surge around ovulation sits a multiple higher than the rest, and in men with one range. Without a cycle day an LH value in women cannot be read: the same value is ordinary mid-surge and too high a week later.

LH is the hormone of the moment. For anyone who wants to become pregnant the LH surge is the window: ovulation follows within one to two days, and that is exactly what an ovulation test measures. For anyone who wants to understand the cycle, LH together with FSH shows whether the brain is driving the ovaries normally. Two patterns are worth knowing. In PCOS, LH often stands raised while FSH stays normal, and that skewed ratio goes with the missing ovulation, the higher androgens and the insulin resistance that characterise the syndrome; losing weight around the middle and less sugar and fast carbohydrates are the levers there. With eating too little, training a lot, fast weight loss or lasting stress the opposite happens: LH and FSH drop away together, ovulation stays away and oestradiol falls. Periods stop or become irregular, and in a sporty woman that is not fitness but a deficit. In men LH is the value that makes a low testosterone readable. Low testosterone with a low LH is almost always the signal from the brain: excess weight, sleep apnoea, long-term stress, some medicines, and anabolic steroids, which shut the pituitary down. Low testosterone with a high LH is testes making less, with age or after damage. The first can usually be reversed with lifestyle, the second cannot, and LH is the number that keeps the two apart. For diagnosing the menopause LH, like FSH, is less suitable than it seems: it fluctuates in the years before, and the menopause is diagnosed on symptoms and the absence of periods.

A high LH in women is usually timing: the surge around ovulation, or the years after the menopause, in which LH like FSH stays permanently higher. Beyond those it is usually PCOS, with an LH higher than the FSH beside it. In men a high LH means testes making less testosterone, so that the pituitary asks harder. A low LH is the ordinary picture at the start and in the second half of the cycle, and on the pill the intention. Beyond those, together with a low FSH and oestradiol, it points at the signal from the brain: an energy deficit, overtraining, fast weight loss or stress, and rarely the pituitary itself. In men a low LH with a low testosterone is the signal from the brain, and excess weight, sleep apnoea, stress, opioids and anabolic steroids are the usual causes. Where LH is low from an energy deficit, the lever is the balance: more food, especially carbohydrates and fat, fewer training hours, more sleep, no crash diet; count on months. In PCOS losing weight around the middle and less sugar work, because insulin resistance sits beneath the skewed ratio. In men with a low LH, losing weight, sleep and stopping anabolic steroids work; after steroids the recovery of production of your own takes months to more than a year. A high LH from ovaries or testes that no longer respond cannot be reversed with lifestyle. LH belongs beside FSH, and in women beside the cycle day and oestradiol; progesterone a week later shows whether ovulation really happened. In men testosterone belongs beside it. And for questions about the signal from the brain, have blood drawn in the morning, because LH is released in pulses and is most stable in the morning.