The yellow-pigmented glandular structure that forms from the ovarian follicle following ovulation. The gland produces progesterone, which is responsible for preparing and supporting the uterine lining for implantation. Progesterone also causes the half-degree basal temperature elevation noted at midcycle during an ovulatory cycle. If the corpus luteum functions poorly, the uterine lining may not support a pregnancy. If the egg is fertilized, a corpus luteum of pregnancy forms to maintain the endometrial bed and support the implanted embryo. A deficiency in the amount of progesterone produced (or the length of time it is produced) by the corpus luteum can mean the endometrium is unable to sustain a pregnancy. This is called Luteal Phase Defect (LPD).