LH
Also called Luteinizing hormone, lutropin
LH (luteinizing hormone) is a hormone made by the pituitary gland that signals the reproductive glands. In men, LH tells the testicles to make testosterone. In women, LH helps control the menstrual cycle, and a sharp rise just before ovulation triggers the release of an egg.
LH works in a feedback loop: testosterone and estradiol signal the brain to hold LH back. When the testicles are not responding, LH tends to run high; when the problem lies in the pituitary or hypothalamus, LH tends to be low or inappropriately normal despite low testosterone. That is why LH is read with testosterone, and usually with FSH (follicle-stimulating hormone).
Why it matters after 45
For men with low testosterone, both the American Urological Association and the Endocrine Society call for measuring LH, because it separates primary hypogonadism (a testicular cause) from secondary hypogonadism (a pituitary or hypothalamic cause), which points the further evaluation in a different direction. The AUA adds a prolactin test when LH is low or low-normal. In women, rising LH and FSH are a normal part of perimenopause and menopause.
Where it comes up
Related terms
References
- MedlinePlus. Luteinizing Hormone (LH) Levels Test. U.S. National Library of Medicine. https://medlineplus.gov/lab-tests/luteinizing-hormone-lh-levels-test/
- American Urological Association. Evaluation and Management of Testosterone Deficiency (AUA Guideline). https://www.auanet.org/guidelines-and-quality/guidelines/testosterone-deficiency-guideline
- Endocrine Society. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline, 2018. https://www.endocrine.org/clinical-practice-guidelines/testosterone-therapy
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