Luteinizing Hormone (LH)

Luteinizing hormone (LH) is a chemical messenger made by the pituitary gland in the brain that plays a key role in reproduction. In women, a sudden rise in LH triggers the release of an egg each month (ovulation), while in men it signals the testes to make testosterone. Doctors measure LH to help understand fertility issues, irregular periods, early or delayed puberty, and hormonal imbalances. Both too-high and too-low LH levels can indicate different problems with the reproductive system or the glands that control it. Results are always interpreted together with other hormone tests and your personal health history.

When elevated: Elevated LH in the context of low sex steroids suggests primary gonadal failure (hypergonadotropic hypogonadism), as seen in premature ovarian insufficiency, Klinefelter syndrome, or post-gonadectomy states. A markedly elevated midcycle LH in females is physiologically normal and represents the ovulatory surge. Persistently elevated LH with an elevated LH:FSH ratio may indicate PCOS. Elevated LH can also be seen in complete androgen insensitivity syndrome and in postmenopausal women as a normal physiological finding. When low: Low LH in the setting of low sex steroids indicates hypogonadotropic hypogonadism, pointing to hypothalamic or pituitary dysfunction. Causes include functional hypothalamic amenorrhea, hyperprolactinemia, pituitary adenomas, Kallmann syndrome, and systemic illness. Low LH may also reflect suppression from exogenous sex steroid administration or anabolic steroid use. In prepubertal children, low LH is physiologically normal.

LH is relevant to athletes because it regulates testosterone production in males and ovulation/progesterone in females—both critical for muscle recovery, energy metabolism, and training adaptation. Abnormal LH levels may indicate overtraining syndrome, hormonal imbalance, or reproductive dysfunction that can impair performance and recovery; tracking it helps athletes and coaches assess whether training load is sustainable.