Luteinizing Hormone (LH)

By RRM Academy Reviewed by Dr. Naomi Whittaker, MD, Board-Certified OBGYN, MIGS, NFPMC, FCI Updated May 13, 2026

Luteinizing Hormone (LH) is a glycoprotein gonadotropin secreted by the anterior pituitary in a pulsatile pattern, responsible for two essential events: the mid-cycle LH surge that triggers the ovulatory cascade, and ongoing stimulation of the corpus luteum to produce progesterone after ovulation.

The LH surge initiates follicle rupture within 36 to 40 hours. Urinary ovulation predictor kits detect this surge and are commonly used to estimate fertile-window timing. Surge detection alone does not confirm ovulation. In LUF syndrome, the surge occurs normally while the follicle fails to rupture. A follicle maturation study using serial ultrasound confirms actual follicle rupture; an LH test cannot.

Basal LH on cycle day 2 or 3 is part of an RRM hormonal panel. An elevated LH-to-FSH ratio is one finding consistent with PCOS. Persistently elevated LH outside the expected surge window can reflect hypothalamic disruption, stress, or thyroid dysfunction. Without cycle chart data anchoring the timing, a single LH value is difficult to interpret. That is the clinical problem with random-day hormone draws. Chart-based evaluation removes that ambiguity.

LH is also relevant in male reproductive evaluation. In men, pulsatile LH stimulates Leydig cells to produce testosterone. Evaluation of the male partner includes LH alongside FSH and testosterone when spermatogenesis is abnormal.

This content is for educational purposes only and does not constitute medical advice. Consult an RRM clinician or healthcare provider for guidance specific to your situation.