Detailed definition
Luteinizing hormone (LH) is a glycoprotein gonadotropin produced by the same pituitary cells as FSH. During the reproductive cycle, a sharp midcycle LH surge — driven by rising estradiol crossing a threshold for positive feedback — triggers ovulation. After ovulation, LH supports the corpus luteum and its production of progesterone. After menopause, when ovarian feedback is absent, LH remains chronically elevated, typically above 20 mIU/mL. In men, LH stimulates Leydig cells to produce testosterone. LH measurement is sometimes paired with FSH and estradiol when working up amenorrhea, primary ovarian insufficiency, polycystic ovary syndrome, or pituitary disorders. Like FSH, LH is not required to make a clinical diagnosis of perimenopause or menopause when symptoms and cycle history are typical.
Why it matters in menopause
For most women presenting with hot flashes, night sweats, and irregular cycles in their 40s, LH and FSH testing is unnecessary and may mislead. The two situations where LH measurement adds value: working up POI in women under 40 (paired with FSH and estradiol), and confirming menopause in women who have had a hysterectomy and therefore no longer have menstrual cycles to track.