NAPLEX Contraception And Infertility Practice Test

Progesterone is the dominant hormone during the luteal phase. After ovulation, the ruptured follicle becomes the corpus luteum, which primarily secretes progesterone (with some estrogen). This progesterone drives the endometrium into a secretory state, preparing it for possible implantation and helping sustain a early pregnancy. It also provides negative feedback to the hypothalamus and pituitary, reducing GnRH and suppressing further LH and FSH to prevent another ovulation this cycle. Estrogen is present but its effect is secondary during this phase, while LH and FSH are relatively low after the ovulation trigger. If pregnancy occurs, hCG from the implanted embryo maintains the corpus luteum and progesterone production; if not, the corpus luteum regresses, progesterone falls, and menses begins.