Why measure around Day 2?Īt this time, E2 is at its lowest so FSH should be at its highest. Some E2 reaches the blood to cause the lining of the uterus to grow, the secretion of ovulatory cervical mucus, and to provide feedback to the brain and pituitary that another cohort of follicles has been recruited and is growing. The level of FSH then falls due to negative feedback by E2. What is E2?Į2 is the steroid hormone that is produced by the cells lining the ovarian follicles in response to FSH, and the very high levels of E2 within the leading follicle nourish and mature the egg. If more FSH than 9iu/l is produced at the time of a period, the brain has somehow realised that to stimulate follicles to grow, more FSH is required than is normal – and the usual reasons for this are that the number of follicles in the ovary is low, or there is some problem within the follicles that the FSH needs to overcome to stimulate another menstrual cycle. When the brain realises that there is low E2 around (ie at the time of a period), and a further group of follicles should be recruited to start another cycle, the blood level of FSH rises, but generally to not more than 9iu/l. What is FSH?įSH is Follicle Stimulating Hormone, and it is produced by the brain (via the pituitary gland) to stimulate follicles in the ovary to grow.

This is sometimes abbreviated to “Basal FSH measurement” but would be better described as “FSH measurement when the E2 is Basal” (ie at the time of a period). FSH, E2 & Progesterone A quick summary about FSH, E2 and Progesterone - when to test and why.

10 day follicular phase