Luteinizing hormone (LH): definition and meaning
Luteinizing hormone (LH) is a hormone made by the pituitary gland at the base of the brain. In people with ovaries, it works with FSH to mature an egg, then a sharp LH surge triggers ovulation and turns the empty follicle into the corpus luteum, which makes progesterone. Ovulation tests detect LH in urine.
What LH does across the cycle
| Phase | LH level | What it does |
|---|---|---|
| Follicular | Low to moderate | Helps the follicle make estrogen |
| Ovulation | Sharp surge | Triggers the egg's release |
| Luteal | Low | Supports the corpus luteum and progesterone |
LH is controlled by gonadotropin-releasing hormone from the hypothalamus, and by feedback from estrogen and progesterone. Its partner hormone is follicle-stimulating hormone.
LH tests
- Urine tests: home ovulation predictor kits look for the LH surge.
- Blood tests: doctors check LH, often with FSH, to look into irregular periods, fertility, PCOS or menopause.
In PCOS, LH is often higher than FSH. After menopause, LH and FSH stay high because the ovaries no longer respond.
LH and how you feel
LH itself isn't known to change mood directly, but the surge sits right at the estrogen peak, which many people notice as their most energetic, social days. See the ovulation phase.
LH also matters later in life. As the ovaries run low on eggs in perimenopause, the brain sends out more FSH and LH to push them, so levels creep up and swing. Those swings help explain why cycles, sleep and mood can all feel less predictable in your 40s.
Frequently asked questions
What is a normal LH level?
It depends on the cycle day and the lab. It is low for most of the cycle and can rise several-fold during the surge, so results are always read alongside the day they were taken.
Is LH the same as hCG?
No, but they are similar molecules. That's why some ovulation tests can react to pregnancy hormone.
Can LH be too high?
Persistently high LH can be seen in PCOS and after menopause, and in premature ovarian insufficiency. A doctor reads LH together with FSH, estrogen and your cycle history rather than on its own.
Sources
This page is for information only and isn’t medical advice. If something worries you, please talk to a doctor.
Keep reading
What is the LH surge?The LH surge is a sharp rise in luteinizing hormone that triggers ovulation about 24 to 36 hours later. Timing, testing, and what it means for fertility.
Follicle-stimulating hormone (FSH): definitionFSH is the pituitary hormone that makes ovarian follicles grow. What it does in your cycle, what high or low FSH means, and how it changes near menopause.What is an ovulation predictor kit (OPK)?An ovulation predictor kit (OPK) is a home urine test that detects the LH surge before ovulation. How OPKs work, when to test, and how to read them.
Menstrual cycle hormones: a simple chart of what rises and fallsMenstrual cycle hormones explained simply: how estrogen, progesterone, LH and FSH rise and fall through each phase, and how they shape mood and energy.Ovulation test calculator: when to start testingFree ovulation test calculator: enter your last period and cycle length to see the day to start LH tests, plus the best time of day to test. Any brand.