During the natural menstrual cycle, pituitary gland cyclically synthesizes follicle stimulating hormone (FSH) and luteinizing hormone (LH) which facilitates growth and development of oocytes in a follicular fluid-filled sac called the follicle. At the beginning of each menstrual cycle, several follicles begin to grow, but only one reaches a mature level and releases an egg. Ovulation or egg release from the ovaries is provided by the LH elevation mid-cycle. During an IVF procedure, a nurse will teach you to inject the same hormones – FSH/LH, which are cyclically emitted by the female body, only in a higher dose, as our aim is to stimulate the growth of several eggs in each ovary.
If your doctor has chosen egg stimulation with agonists or “long protocol”, you will receive a so-called blocking vaccine with a GnRH agonist on menstrual cycle day 2-23 (about a week before menstruation). This injection would subside the natural FSH/LH production at the pituitary gland.