What Is Luteinizing Hormone? Definition

Luteinizing hormone (LH) is a hormone made by the pituitary gland in your brain. It plays a central role in reproduction for both men and women. In women, LH triggers ovulation — the release of an egg from the ovary. In men, LH signals the testes to produce testosterone.

What Does Luteinizing Hormone Do?

LH acts like a messenger between your brain and your reproductive organs. It belongs to a group of hormones called gonadotropins, which also includes follicle-stimulating hormone (FSH). Together, LH and FSH control the menstrual cycle in women and sperm production in men.

In women: LH levels rise sharply in the middle of the menstrual cycle. This surge, which lasts about 24 to 36 hours, causes the ovary to release a mature egg. After ovulation, the empty follicle turns into the corpus luteum, which produces progesterone to prepare the uterus for a potential pregnancy. If no pregnancy occurs, LH levels drop and a new cycle begins.

In men: LH stimulates Leydig cells in the testes to produce testosterone. Testosterone is essential for sperm production, sex drive, muscle mass, and bone density. LH release in men is relatively steady, not cyclic.

In children: LH levels are low before puberty. During puberty, the brain increases LH production, which triggers the development of secondary sexual characteristics such as breast growth in girls and facial hair in boys.

What Is a Normal LH Level?

Normal LH levels depend on your age, sex, and — for women — where you are in your menstrual cycle. Laboratories report ranges in international units per liter (IU/L). There is no single “normal” number that applies to everyone.

Adult women (premenopausal):

• Follicular phase (days 1–14): about 1–20 IU/L
• Ovulation peak: about 20–100 IU/L
• Luteal phase (after ovulation): about 1–20 IU/L

Postmenopausal women: LH levels are typically high — often above 20 IU/L. This happens because the ovaries no longer produce estrogen, so the pituitary gland increases LH production to try to stimulate them.

Adult men: Typical LH levels range from about 1–10 IU/L. Levels vary with age and health.

Children: LH is normally very low (under 0.3 IU/L) before puberty begins.

These are general reference ranges. Different laboratories may use slightly different values. Always discuss your results with a doctor.

What Happens When LH Is Too High?

High LH levels often signal that the reproductive organs are not responding to hormone signals. The pituitary gland works harder to compensate.

In women:

• Menopause: LH rises because the ovaries stop producing estrogen. This is normal and expected.
• Polycystic ovary syndrome (PCOS): Many women with PCOS have a higher LH-to-FSH ratio. The LH level may be elevated while FSH stays normal or low.
• Primary ovarian insufficiency: The ovaries fail to respond to LH, so the pituitary keeps sending more.

In men:

• Primary testicular failure: Damage to the testes from injury, infection, chemotherapy, or genetic conditions causes LH levels to rise.
• Klinefelter syndrome: A genetic condition where men have an extra X chromosome, leading to small testes and low testosterone with high LH.

In children:

• High LH before age 8–9 in girls or age 9–10 in boys may indicate central precocious puberty — puberty that starts too early.

What Happens When LH Is Too Low?

Low LH levels suggest the pituitary gland is not producing enough stimulation. This can affect fertility and hormone production.

In women:

• Hypothalamic amenorrhea: Caused by stress, low body weight, or excessive exercise. The brain stops producing GnRH, which shuts down LH and FSH. Periods stop.
• Pituitary disorders: Tumors, injury, or rare genetic conditions (like Kallmann syndrome) reduce LH production.
• Anorexia nervosa: Severe caloric restriction can suppress the entire reproductive hormone axis.

In men:

• Secondary hypogonadism: The problem is in the pituitary or hypothalamus, not the testes. LH is low, testosterone is low, and sperm production suffers.
• Prolactinoma: A pituitary tumor that secretes prolactin can suppress LH.
• Opioid use: Opioid medications can lower LH and testosterone.

In children:

• Low LH at the expected age of puberty may indicate delayed puberty or a condition causing no puberty at all.

How Is Luteinizing Hormone Tested?

LH is measured with a blood test. A healthcare provider draws blood from a vein, usually in your arm. The sample is sent to a lab for analysis.

Timing matters for women: Because LH levels change throughout the cycle, doctors often test LH on specific days. Day 3 of the menstrual cycle is a common starting point to assess ovarian reserve. To confirm ovulation, they may test around day 14 or look for a surge.

Urine tests for ovulation prediction: Home ovulation predictor kits detect the LH surge in urine. They are accurate for timing intercourse or insemination. However, they do not measure exact LH levels — they give a positive or negative result.

Random testing in men: LH can be drawn at any time of day. Testosterone levels fluctuate slightly, so some doctors prefer a morning sample.

LH is often tested together with FSH, estrogen, progesterone, and testosterone to get a fuller picture of reproductive health.

What Affects LH Levels?

Several factors can temporarily or permanently change LH levels. It is important to interpret results with your lifestyle and medical history in mind.

• Stress: Both physical and emotional stress can suppress the hypothalamic-pituitary-gonadal axis, lowering LH.
• Exercise: Very high levels of exercise, especially endurance training, can lower LH in both men and women.
• Body weight: Being significantly underweight or obese can disrupt LH production. Fat cells produce estrogen, which feeds back to the pituitary and can suppress LH.
• Medications: Birth control pills, hormone replacement therapy, opioids, corticosteroids, and some antipsychotics can affect LH levels.
• Age: LH rises naturally with menopause and andropause (declining testosterone in older men).
• Circadian rhythm: LH has a pulsatile pattern. In men, morning LH is often slightly higher. In women, pulse frequency changes across the cycle.

No single factor determines LH level alone. Multiple influences often combine.

Luteinizing Hormone and Fertility Treatment

LH plays a direct role in fertility treatments. In some cases, doctors give LH-like medications to trigger ovulation or support egg development.

Ovulation induction: For women who do not ovulate on their own, injectable medications containing LH or human chorionic gonadotropin (hCG) can trigger egg release. hCG acts similarly to LH and is used for “trigger shots.”

In vitro fertilization (IVF): During IVF, high doses of LH are given (often through a combination of FSH and LH medications) to stimulate multiple egg follicles. Doctors monitor LH levels and adjust medication doses.

For men: If low LH is caused by a pituitary problem (hypogonadotropic hypogonadism), LH injections can stimulate testosterone production and sperm production. This is a specialized treatment typically managed by a reproductive endocrinologist.

Fertility drugs that contain LH or mimic its action include human menopausal gonadotropin (hMG) and recombinant LH. These are prescription-only medications with specific dosing protocols.

Key Takeaways About Luteinizing Hormone

Luteinizing hormone is essential for normal reproduction. It drives ovulation in women and testosterone production in men. Levels are carefully regulated by the brain and feedback from sex hormones.

Abnormal LH levels can point to underlying health issues such as PCOS, menopause, pituitary disorders, or fertility problems. But a single test result is rarely enough for a diagnosis. Doctors look at your symptoms, other hormone levels, and overall health.

If you have concerns about your LH levels or your fertility, talk to a healthcare provider. They can order the right tests and explain what your results mean for you specifically.