Luteal phase

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The luteal phase is the last phase of the menstrual cycle. The menstrual cycle is on average 28 days in length, beginning with menses (day 1–7) during the follicular phase (day 1–14), followed by ovulation (day 14) and ending with the luteal phase (day 14–28). The luteal phase was thought to be relatively fixed at approximately 14 days, but studies now suggest that there can be wide variability in luteal phase lengths not just from person to person, but from cycle to cycle within one person. The luteal phase is characterized by changes to hormone levels, such as an increase in progesterone and estrogen levels, decrease in gonadotropins such as follicle-stimulating hormone (FSH) and luteinizing hormone (LH), changes to the endometrial lining to promote implantation of the fertilized egg, and development of the corpus luteum. In the absence of fertilization by sperm, the corpus luteum degenerates leading to a decrease in progesterone and estrogen, an increase in FSH and LH, and shedding of...

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