luteal

Luteal is an adjective used in anatomy and physiology to refer to the corpus luteum or to the luteal phase of the ovarian cycle. In humans and many mammals, the luteal phase follows ovulation and typically lasts about 12 to 14 days.

After ovulation, the ruptured follicle is transformed into the corpus luteum, a temporary endocrine gland. The corpus luteum is composed of luteal cells derived from granulosa and theca interna cells. It secretes progesterone as its principal product, along with smaller amounts of estrogen and inhibin. Progesterone acts on the endometrium to promote secretory changes and maintain conditions suitable for implantation and early pregnancy.

Regulation: Luteal function is supported mainly by luteinizing hormone (LH) from the pituitary. In pregnancy, human chorionic gonadotropin (hCG), produced by the implanted embryo, binds to the same receptor and prolongs corpus luteum function, a process known as luteal rescue. If fertilization does not occur, the corpus luteum degenerates in a process called luteolysis around day 14, progesterone and estrogen levels fall, the endometrium sheds, and a new cycle begins with menses. The degenerated tissue becomes corpus albicans.

Clinical and comparative notes: Luteal phase length is relatively constant across cycles, and problems in luteal function are sometimes described as luteal phase deficiency, though the concept is debated. Luteal insufficiency can be implicated in infertility or recurrent pregnancy loss in some contexts. Across species, luteolysis may be triggered by prostaglandins and differs in timing and mechanism, but the general pattern of a progesterone-rich luteal phase remains common.