LH (Luteinizing Hormone)
LH is released by the anterior pituitary in pulses. In women, the LH surge in mid-cycle triggers ovulation; LH also stimulates corpus luteum progesterone production. In men, LH drives testicular testosterone production. LH is tested alongside FSH in fertility evaluation, PCOS diagnosis (classical LH:FSH ratio >2:1), central precocious puberty, and hypogonadism workup. Because LH is pulsatile, a single sample can be misleading — repeat sampling is sometimes needed.
Reference Ranges
Male
1.7 – 8.6
mIU/mL
Female
2.4 – 12.6
mIU/mL
Child
Consult pediatrician
Reference ranges may vary by laboratory. Always compare with the range printed on your lab report.
What Low Levels Mean
Low LH with low estradiol in women, or low LH with low testosterone in men, suggests central (pituitary or hypothalamic) dysfunction. Causes include pituitary adenoma, hyperprolactinemia, hemochromatosis, hypothalamic amenorrhea (stress, anorexia, over-exercise), and Kallmann syndrome. Oral contraceptives suppress LH. Pituitary MRI is often part of the workup.
What High Levels Mean
In women, an elevated LH:FSH ratio (>2:1) is a classical PCOS finding (though not required for diagnosis). Very high LH with amenorrhea is seen in premature ovarian insufficiency and menopause. In men, elevated LH with low testosterone indicates primary (testicular) failure. In children, premature elevation of LH suggests central precocious puberty and needs specialist workup.
Frequently Asked Questions
How does LH relate to ovulation?
A surge of LH — lasting roughly 24–36 hours in mid-cycle — triggers ovulation about 36 hours after surge onset. Ovulation predictor kits detect this LH surge in urine to time intercourse or insemination. Serum LH and progesterone confirm ovulation after the fact; urine LH kits predict it in advance.
What is the LH:FSH ratio in PCOS?
An LH:FSH ratio greater than 2:1 is a classical (though not required) feature of PCOS. Modern PCOS diagnosis uses the Rotterdam criteria: 2 of 3 — oligo/anovulation, clinical or biochemical hyperandrogenism, polycystic ovarian morphology on ultrasound — after excluding other causes. Not all PCOS patients have an elevated LH:FSH ratio.
Why is LH measured in children?
To evaluate precocious puberty. Central (gonadotropin-dependent) precocious puberty shows elevated LH on GnRH stimulation testing. Peripheral precocious puberty (from ovarian or adrenal sources) shows suppressed LH. Treatment (GnRH analog therapy) depends on this distinction. Specialist pediatric endocrinology input is essential.
Related Hormones tests
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Pancreatic hormone that controls blood sugar.
µIU/mLHormonesHOMA-IR (Insulin Resistance Index)
Calculated index that estimates insulin resistance.
indexHormonesBeta-hCG (Human Chorionic Gonadotropin)
Pregnancy hormone — also a tumor marker for certain cancers.
mIU/mLHormonesSex Hormone Binding Globulin (SHBG)
Protein that binds sex hormones in blood, controlling their availability.
nmol/LThis information is for educational purposes only and should not replace professional medical advice. Always consult your doctor for interpretation of your test results.
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