Luteinizing Hormone
A pituitary hormone that triggers testosterone production in men and ovulation in women.
| Typical reference range (male) | 1.5–9.3 mIU/mL |
Ranges vary by laboratory, method, age and sex: always use the range printed on your own report. Why labs differ.
What it measures
LH is released by the pituitary in pulses in response to GnRH from the hypothalamus. In men it stimulates the testes' Leydig cells to make testosterone; in women a mid-cycle surge triggers ovulation.
Why it matters
LH helps determine whether low sex hormones originate in the gonads (high LH, primary) or the pituitary/hypothalamus (low or normal LH, secondary). It is also used in fertility, PCOS and menopause assessment.
What a high result can mean
High LH occurs with primary testicular or ovarian failure, menopause, PCOS (often with LH/FSH ratio above 2) and at the mid-cycle surge.
What a low result can mean
Low LH occurs with testosterone, anabolic steroid or hormonal contraceptive use, pituitary or hypothalamic disorders, high prolactin, low body weight, intense exercise, opioid use and severe stress.
What affects the result
Released in pulses, so a single value can vary. In women, levels depend heavily on cycle phase (roughly 2-15 follicular, 20-100 at the surge, above ~15 postmenopausal). Exogenous testosterone suppresses LH to near zero.
Units and conversion
Usually reported in mIU/mL.
- From IU/L: multiply by 1 to get mIU/mL
- From mIU/L: multiply by 0.001 to get mIU/mL
Also called on lab reports
LH, Luteinizing Hormone (LH), LH, Serum
Related tests: Sex Hormones
This page is educational and does not replace advice from a healthcare professional.