what is the luteal phase

The luteal phase is a phase of the menstrual cycle that occurs after ovulation and before the next period. It typically lasts about 14 days, although there is a broad range of what is considered normal. During this phase, the corpus luteum, which is the empty follicle left in the ovary after an egg has been released, produces progesterone that helps thicken the lining of the uterus in preparation for a possible pregnancy. The luteal phase is characterized by changes in hormone levels, such as an increase in progesterone and estrogen levels, and a decrease in gonadotropins such as follicle-stimulating hormone (FSH) and luteinizing hormone (LH) . The endometrial lining also changes to promote implantation of the fertilized egg, and the corpus luteum continues to grow and produce significant amounts of hormones, particularly progesterone, and to a lesser extent, estrogen and inhibin. A short luteal phase is defined as being 11 days or fewer from the day of ovulation to the first day of the next period, which may not give the womb lining enough time to thicken sufficiently to support implantation of a fertilized egg. On the other hand, a long luteal phase means that the period comes 18 days or later after ovulation, which may indicate a hormonal imbalance like polycystic ovary syndrome (PCOS) .