LH

LH is the signal behind ovulation and the signal that keeps a man's testes making testosterone. When your ovaries or testes start to slip, LH can move while testosterone or estradiol still looks normal.

It is also one of the few hormones that reads differently depending on who you are. A high value that spells trouble in a 60-year-old man can be completely normal in a woman the same age. The number only helps if you read it in context.

What LH Actually Is

LH stands for luteinizing hormone. It is a protein hormone released by a small cluster of cells in your pituitary gland. The pituitary is the control gland at the base of your brain.

Those cells respond to pulses of a signal from the hypothalamus just above them. In many settings, the pulses come roughly every 60 to 90 minutes, but the rhythm changes across the menstrual cycle.

The system works as a feedback loop from brain to pituitary to ovaries or testes. Your ovaries or testes make sex hormones, and those hormones tell the pituitary to ease off. So the LH level in your blood reflects how hard your pituitary is working to get a response. Read it that way and both high and low results start to make sense.

What High and Low Levels Mean

Outside the mid-cycle surge, high LH means the pituitary is shouting. In women, that often means the ovaries are winding down, which is the normal picture in menopause and can be the early picture in premature ovarian insufficiency. In men, high LH points to the testes failing to keep up, from causes like prior chemotherapy, radiation, or Klinefelter syndrome. Polycystic ovary syndrome can be an exception: LH may run high relative to FSH while the ovaries are still working.

Low LH means the signal itself is missing. When the brain or pituitary stops sending the command, sex hormones fall but LH stays low or low-normal instead of rising to compensate. In women this shows up as functional hypothalamic amenorrhea, often from stress, under-eating, or heavy training, and in men as secondary hypogonadism from a pituitary or hypothalamic problem. The pattern that matters is whether LH is high or low when your sex hormones are low, because that single distinction separates an ovary or testis problem from a brain signal problem.

What Rising LH Predicts in Men

In older men, a creeping LH can be a warning sign even when testosterone still looks normal. The pattern has a name: compensated Leydig cell dysfunction. Leydig cells are the testicular cells that make testosterone. In this pattern, the testes are struggling and the pituitary is working harder to prop up testosterone.

A Danish study followed about 5,350 men for up to 30 years. Men in the top quarter of LH were roughly a third more likely to die of any cause than men in the bottom quarter, and about 42% more likely to die of cancer, and these links held after accounting for smoking and other risk factors. A large pooled analysis of hundreds of thousands of person-years found the same direction: men with LH above 10 units per liter had higher death rates after adjusting for age, weight, smoking, blood pressure, diabetes, and cholesterol. A separate cohort of men in their 70s and 80s found higher LH predicted heart attacks and other heart events.

The cancer link is less simple than the older Danish data suggested. A newer pooled analysis found LH tied to cancer death in a U-shaped way, with mid-range LH carrying the lowest risk and lower LH associated with higher prostate cancer risk. What holds across studies is that a rising LH with still-normal testosterone is not something to shrug off as just aging. It is worth tracking, because it tends to travel with declining health rather than causing it. It can flag a body under more strain than a single testosterone reading suggests.

The Metabolic Picture in Women Runs the Other Way

In women after menopause, the LH story flips. A 5-year study of 114 postmenopausal women found lower LH was tied to later insulin resistance and diabetes risk, though FSH was the stronger signal and LH was not clearly tied to new impaired fasting glucose. An analysis of about 3,831 women found that in postmenopausal women, higher LH was tied to about 18% lower odds of metabolic syndrome. In men higher LH looks worse; in these women it looks better or neutral.

That contradiction resolves once you stop treating LH as a good-number-bad-number test. It is a readout of the reproductive axis, and the same reading carries different meaning depending on why the axis is behaving that way. In an aging man, high LH usually signals failing testes, which tracks with worse health. In a postmenopausal woman, high LH is the expected state after the ovaries have stopped cycling. Same number, different story.

Fertility and the Ovulation Trigger

For anyone trying to conceive, LH is central. Its mid-cycle surge is the direct trigger for the ovary to release an egg, which is why home ovulation kits measure LH in urine. Too much or too little can be part of disrupted fertility: in PCOS, LH often runs high relative to FSH and cycles become unpredictable, while in hypothalamic amenorrhea LH runs too low to drive ovulation at all.

In men, LH is one step upstream of the testosterone that sperm production depends on, so an abnormal level helps explain low sperm counts and points to whether the problem is in the testes or in the brain. Paired with FSH and a sex hormone, it turns a vague fertility problem into a specific one you can act on.

Why One Reading Is Not Enough

LH is the most variable of the common reproductive hormones. Its typical swing within the same person is about 26 to 28% from one measurement to the next, because it is released in pulses rather than at a steady level. Draw blood at a peak and it looks high; draw it at a trough an hour later and it looks normal. Morning values also run about 18% above the daily average.

This is why a single number can mislead in both directions, and why two or three measurements beat one. In women, the reading also depends heavily on where you are in your cycle, since LH is low in the follicular and luteal phases and spikes at mid-cycle. A good approach is a baseline, a repeat if the first result is surprising or you are making changes, and periodic rechecks rather than betting a decision on one draw.

Tracking also tells you whether something is actually shifting. A slow climb in a man's LH across annual checks is a different signal than a single high value. Around menopause, LH can support the pattern, but it should not be used alone.

When a Single Result Can Fool You

• Biotin supplements: high-dose biotin, common in hair and nail products, can push LH readings falsely high or low in some lab assays. Stop it at least 72 hours before the draw unless your test instructions say otherwise.
• Recent hCG trigger shots or pregnancy: hCG can confuse home LH strips, and very high hCG can interfere with some LH blood assays. Tell the lab if you are pregnant or recently used hCG.
• Acute illness or recent surgery: serious illness and the stress of an operation can suppress LH for days to weeks, and the drop tracks with how sick you are, not with a true reproductive problem.
• Severe under-fueling or advanced kidney disease: days of a large calorie deficit lower LH pulses, while advanced kidney disease can change LH clearance and pulse patterns.

What to Do With an Unexpected Result

LH almost never stands alone. The move after a surprising value is to repeat it, given how much it varies, and to pair it with FSH and a sex hormone, testosterone in men or estradiol in women. The combination tells you whether a low sex hormone comes from the ovaries or testes, with LH high, or from the brain signal above them, with LH low or normal.

Draw it at the same time of day, ideally morning, and not during an acute illness. Fast if you are pairing it with testosterone or metabolic labs. If the pattern points to a central cause, prolactin, thyroid tests, and sometimes iron studies help find why, and a pituitary workup may follow. From there the right specialist depends on the picture: a reproductive endocrinologist for fertility, an endocrinologist for a suspected pituitary problem, and a urologist for male-factor infertility. The useful answer is a pattern across several markers, not a verdict from one number.