The luteinizing hormone (LH) is secreted by the pituitary gland involved in the control of ovulation. The role of LH is to trigger ovulation and help prepare the endometrial lining for implantation. The level of this hormone starts to rise roughly 24 hours prior to expected ovulation. We can check this by using a home ovulation predictor kit, such as Clear Blue Easy. When the test color matches the control, this signifies the presence of elevated levels of LH in the blood. The individual then can plan intercourse or IUI within 24 hours of that positive test.