Luteinizing hormone
Also known as: LH
Medically reviewed by Hormone Journal Editorial Team · Last reviewed 2026-05-17
Luteinizing hormone (LH) is a pituitary hormone that triggers ovulation in females and testosterone production in males.
What it is
Luteinizing hormone (LH) is a pituitary hormone that triggers ovulation in females and testosterone production in males. It is a glycoprotein — a protein with sugar chains attached — made up of two subunits (alpha and beta) with a combined mass of about 28 kDa. LH is released by gonadotroph cells in the anterior pituitary gland, which make up roughly 10–15% of that gland's functional cell mass. It works alongside follicle-stimulating hormone (FSH) as part of the hypothalamic-pituitary-gonadal (HPG) axis, the signaling chain that connects the brain to the reproductive organs.
Causes and mechanism
The hypothalamus releases gonadotropin-releasing hormone (GnRH) in pulses, which prompts the pituitary to secrete LH. In females, rising estrogen levels during the follicular phase eventually trigger a sharp LH surge — typically lasting 24–36 hours — that causes a mature follicle to release an egg (ovulation). After ovulation, LH supports the corpus luteum (the follicle's remnant) in producing progesterone. In males, LH stimulates Leydig cells in the testes to synthesize testosterone continuously. Testosterone and estrogen then feed back to the hypothalamus and pituitary to slow GnRH and LH release — a negative-feedback loop that keeps levels in range. Exogenous (externally supplied) testosterone suppresses this loop and can reduce LH to near zero.
Symptoms and diagnosis
Abnormal LH levels rarely cause a single obvious symptom; they usually appear as part of a broader hormonal picture.
Low LH may present as delayed puberty, absent or irregular periods (amenorrhea or oligomenorrhea), low libido, infertility, or hypogonadism (underactive gonads). Causes include pituitary tumors, Kallmann syndrome (a genetic condition combining GnRH deficiency with impaired sense of smell), excessive exercise, low body weight, or use of anabolic steroids or opioids.
High LH in women outside of the expected mid-cycle surge can indicate primary ovarian insufficiency or polycystic ovary syndrome (PCOS). In men, persistently elevated LH alongside low testosterone points to primary hypogonadism (testicular failure).
LH is measured with a standard blood test. Normal reference ranges vary by lab and life stage, but typical adult values are roughly 1–18 IU/L in women (depending on cycle phase) and 1–9 IU/L in men. Because LH is released in pulses, a single measurement can be misleading; clinicians often test LH alongside FSH, estradiol or testosterone, and prolactin for context.
Treatment options
Treatment targets the underlying cause rather than LH itself.
- LH deficiency: Pulsatile GnRH therapy or injectable gonadotropins (containing LH and FSH activity) can restore fertility. Hormone replacement — estrogen/progesterone in women, testosterone in men — addresses symptoms of hypogonadism but does not restore fertility on its own.
- Elevated LH with ovarian insufficiency: Hormone therapy manages symptoms; fertility options include donor eggs.
- PCOS with elevated LH/FSH ratio: Lifestyle changes, combined oral contraceptives, or ovulation-induction agents (e.g., letrozole, clomiphene) are first-line depending on the goal.
- Suppressed LH from exogenous testosterone: Stopping or adjusting the testosterone dose typically allows LH to recover, though recovery time varies.
When to see a clinician
Request an LH test if you are experiencing irregular or absent periods, signs of early menopause before age 40, unexplained infertility after 6–12 months of trying to conceive, or symptoms of hypogonadism (fatigue, low libido, loss of muscle mass). Men using testosterone therapy should have LH checked before starting, since exogenous testosterone will suppress it. Any result outside the reference range warrants interpretation alongside FSH and sex-steroid levels by an endocrinologist or reproductive specialist.
FAQs
What is the difference between LH and FSH?
LH and FSH are both pituitary hormones that work together to control reproduction, but they have distinct roles. FSH drives the growth of ovarian follicles in women and sperm production in men, while LH triggers ovulation and stimulates testosterone synthesis. Clinicians typically order both tests together — an FSH:LH ratio above 2:1 is one marker used in evaluating PCOS, though it is not diagnostic on its own.
What does a high LH level mean for a woman?
Outside of the normal mid-cycle surge, a consistently high LH (often above 25 IU/L) in a woman of reproductive age can indicate primary ovarian insufficiency or menopause. An elevated LH alongside a high LH:FSH ratio (greater than 2:1) is also associated with PCOS, though diagnosis requires additional criteria. A clinician will interpret the result in the context of cycle day, symptoms, and other hormone levels.
Can low LH cause infertility?
Yes. LH is required for ovulation in women and for testosterone-driven sperm support in men, so deficiency in either sex can impair fertility. Isolated LH deficiency is rare — it most commonly results from exogenous testosterone use or pituitary disease. Injectable gonadotropin therapy can restore ovulation in many women with LH deficiency, with pregnancy rates that vary widely depending on the underlying cause.
Does LH change with age?
Yes, significantly. In women, LH rises sharply during the menopausal transition as the ovaries become less responsive to gonadotropin signaling; post-menopausal LH levels are typically above 15–30 IU/L. In men, LH tends to rise gradually after age 40 as testicular testosterone output declines. Research also suggests that chronically elevated LH in older adults may have effects beyond reproduction, including possible links to cognitive aging, though this evidence is still preliminary.
Is an LH blood test covered by insurance?
In most cases, yes — LH testing is a standard laboratory test covered by major insurers when ordered for a documented clinical indication such as infertility evaluation, menstrual irregularity, or suspected hypogonadism. Coverage for repeat or monitoring tests may require prior authorization. Check with your insurer and confirm the ordering clinician has documented a diagnosis code, as out-of-pocket costs without coverage can range from roughly $30 to $100 depending on the lab.