The LH (Luteinizing Hormone) test is a cornerstone of reproductive health. It's a key 'messenger' hormone from your brain's pituitary gland. In women, LH is the "ovulation trigger"—it surges 24-36 hours before an egg is released, making this test essential for pinpointing your fertile window. In men, LH is the primary signal that tells the testes to produce testosterone. This test is critical for investigating infertility, irregular periods, and PCOS. A simple blood draw provides this vital, dynamic data, offering clear answers for your family planning and hormonal health.