![]() 2 mg/day for days 1-7, then 4 mg/day for days 8-12, then 6 mg/day from day 13 to transfer). 6 mg daily) or can be increased over time (ie. In the past, a GnRH agonist would be used to prevent the LH surge, but estradiol alone is able to suppress this.Į2 can be administered either as a fixed dose (ie. Estradiol also prevents further follicles from growing because it blocks GnRH and prevents FSH/ LH from being produced. In a medicated FET protocol, the endometrium is first prepared using estradiol (E2) which causes the cells of the endometrium to proliferate. These need to be administered exogenously (from outside the body)! This continues until about 10 weeks of pregnancy, at which point the placenta starts to produce progesterone (taking over the job of the corpus luteum) in the so-called luteo-placenta shift.īirth control is often taken before starting estradiol administration to better manage the timing of the medicated FET cycle. In a medicated FET, complete hormone replacement is needed because there is no follicle here to produce estradiol, and therefore there’s no corpus luteum to produce progesterone. Sometimes you might hear of “ luteal phase support”, and this refers to administering progesterone to mimic the luteal phase as described above. This is called “endometrial preparation”. In frozen embryo transfers, estrogen and progesterone may need to be administered to prepare the endometrium artificially. This causes progesterone levels to drop and triggers menstruation at which point the endometrium is shed and the cycle starts over. If there’s no implantation, then there’s no hCG produced and the corpus luteum eventually degrades. The embryo implants during this phase and begins secreting hCG that signals to the corpus luteum to keep producing progesterone (this continues for about 10 weeks). This maintains the thickened endometrium and transforms its cells and architecture so it can accept an embryo for implantation. The empty follicle is now called the corpus luteum and begins secreting progesterone (P4), so P4 levels begin to rise. The leading follicle ovulates and the egg is released into a fallopian tube.įrom CD15 to CD28 the endometrium is now in the secretory phase (aka the luteal phase). Menstruation and the proliferative phase both occur while the follicle is developing, so CD1-CD14 is can be called the follicular phase.Į2 eventually peaks and this causes an LH surge to trigger ovulation. During this phase, the cells of the endometrium proliferate and thicken. These developing follicles begin to produce estrogen, or more specifically estradiol (E2), which causes the endometrium to enter the proliferative phase (CD6 to CD14). LH/ FSH causes follicles in the ovaries to develop. During this period, GnRH acts on the pituitary gland to secrete LH/FSH. Source: Isometrik, CC BY-SA 3.0, via Wikimedia CommonsĬycle day 1 (CD1) to about day 5 is menstruation. ![]()
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