Luteinizing hormone (LH) is a signaling protein released by the pituitary gland at the base of the brain. It acts as a key messenger to the ovaries or testes. In women, an LH surge triggers ovulation (egg release) and supports progesterone production. In men, LH signals the testes to produce testosterone. Because LH reflects brain-to-gonad communication, LH testing provides insight into fertility, menstrual cycles, menopause, and testosterone-related symptoms.

In premenopausal women, LH rises sharply mid-cycle - often called the “LH surge” - which triggers ovulation. Measuring LH can help pinpoint the ovulation window, making it useful for timing intercourse or guiding fertility treatments. LH results are best interpreted with menstrual history and related hormones such as FSH and estradiol, because normal LH varies widely depending on cycle phase and individual hormonal patterns.

LH testing can reveal ovulation problems that contribute to irregular or absent periods and infertility. Low LH may indicate reduced pituitary signaling that suppresses ovulation and estrogen production. High LH may indicate the pituitary is compensating for ovarian under-response, which can occur in menopause, primary ovarian insufficiency, or sometimes PCOS. Clinicians often pair LH with FSH and estradiol to better assess fertility and cycle function.

Low LH usually suggests inadequate signaling from the pituitary or hypothalamus to the ovaries. This can suppress ovulation and estrogen production, leading to irregular or absent periods and difficulty conceiving. Symptoms may include fatigue and other low-estrogen effects such as bone loss risk over time. Common contributors include chronic stress, low body weight, excessive exercise, pituitary dysfunction, or suppression from external hormones.

In men, LH stimulates the testes to produce testosterone. Low LH can reduce testosterone production and impair sperm maturation, contributing to low libido, erectile changes, fatigue, reduced muscle mass, mood shifts, and decreased bone density. This pattern can occur with hypothalamic or pituitary issues, significant stress, low body weight, excessive exercise, or hormone suppression. Interpreting LH alongside testosterone helps clarify whether symptoms reflect signaling problems versus testicular dysfunction.

High LH often means the pituitary is “working harder” because the ovaries or testes aren’t responding adequately. In women, permanently elevated LH is typical after menopause as ovarian function declines. In reproductive-age women, high LH can be seen in primary ovarian insufficiency and may occur with PCOS (often relative to FSH). In men, high LH suggests testicular insufficiency (primary hypogonadism) with reduced testosterone output.

LH and FSH are pituitary hormones that coordinate reproductive function. LH triggers ovulation and supports progesterone in women, and drives testosterone production in men; FSH supports follicle development in women and sperm production in men. Looking at LH alone can be misleading because levels vary by sex, age, and cycle timing. Interpreting LH with FSH - and often estradiol or testosterone - helps identify patterns such as hypogonadotropic hypogonadism or primary gonadal failure.

LH fluctuates significantly across the menstrual cycle, with a mid-cycle surge that triggers ovulation. Because of these shifts, “normal” LH depends on whether testing occurs in the follicular phase, around ovulation, or the luteal phase, as well as whether someone is premenopausal or postmenopausal. For accurate interpretation, results should be considered alongside cycle day, menstrual history, and related hormones like FSH and estradiol.

Yes. Hormonal contraceptives and pregnancy can suppress LH, and certain medications may also alter pituitary signaling. External hormones can blunt the natural LH surge and change baseline LH readings, which can affect ovulation assessment and interpretation of “low” results. Because LH is sensitive to hormonal context, clinicians commonly review medication use and interpret LH alongside FSH, estradiol, or testosterone for a more accurate picture.

LH testing helps assess whether the brain’s pituitary gland is sending appropriate reproductive signals for age and development. Abnormally low LH can suggest reduced pituitary or hypothalamic signaling, which may contribute to delayed puberty. Elevated LH patterns can indicate the gonads aren’t responding properly, prompting the pituitary to increase LH output. Because puberty evaluation is age-dependent, LH is typically interpreted with FSH and clinical context to assess pituitary, ovarian, or testicular function.