Luteinizing hormone (Lutropin)
HormonesAlso known as: LH, interstitial cell stimulating hormone, ICSH
Luteinizing hormone (LH) is produced by the pituitary gland in the brain.
In women, it triggers ovulation and supports estrogen and progesterone production, while in men it stimulates the testes to produce testosterone.
Why this matters
Abnormal LH levels reveal much about reproductive health. In women, too little can cause irregular cycles or infertility, while very high levels often indicate menopause or ovarian insufficiency. In men, low LH leads to reduced testosterone, lowering energy, muscle mass, and libido. Lifestyle factors such as severe stress, undernutrition, and excessive exercise can suppress LH, while age and certain conditions raise it.
Measuring LH helps assess fertility, hormonal balance, and the function of ovaries or testes.
How this connects to other biomarkers
- In men, elevated LH with low Testosteron, total indicates the testicles themselves are failing (primary hypogonadism); low LH with low testosterone indicates a brain/pituitary cause (secondary hypogonadism).
- In women, an LH/FSH Ratio > 2 in the early follicular phase is a classic finding in PCOS (polycystic ovary syndrome).
- The LH surge mid-cycle triggers ovulation; persistently low LH across the cycle suggests hypothalamic amenorrhea (loss of periods due to stress, low body weight, or excessive exercise).
How often should I test Luteinizing hormone (Lutropin)?
For premenopausal women, baseline LH is drawn on day 2 to 5 of the cycle. For postmenopausal women and men, yearly testing alongside other hormones is appropriate. On hormone therapy, retest 6 to 12 weeks after any dose change.
At baseline / for screening: Once every 12 months from age 35, with cycle phase noted in premenopausal women (typically drawn on day 2 to 5 of a 28-day cycle for baseline). More frequently during perimenopause.
When monitoring an intervention or change: Retest 6 to 12 weeks after starting or adjusting hormone therapy (HRT, oral contraceptives, fertility medication). Cycle phase matters as much as cadence, so match the cycle day across draws for meaningful comparison. In perimenopause, expect significant cycle-to-cycle variability that settles only after menopause is established.
Note: LH is released in pulses, so single readings vary by 50 percent or more within hours. For premenopausal women, draw on day 2 to 5; for trend tracking elsewhere, the average of two readings days apart is more reliable than a single value.
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