What is Oestradiol?

Oestradiol reports what the ovary has done with the FSH and LH signal, not the signal itself. Oestradiol also acts in its own right. It thickens the lining of the womb through each cycle, and it slows the bone loss that goes on throughout adult life.

The brain sets the pulses of FSH and LH, and those pulses are the drive the ovary responds to. Reading oestradiol beside FSH and LH distinguishes a pituitary that is signalling weakly from an ovary that cannot answer a normal signal.

FSH and LH set the follicle growing. After that, how much oestradiol appears follows the follicle's size, since the cells that make it sit in the follicle wall and a larger follicle holds more of them.

In those who have a menstrual cycle, oestradiol traces the shape of the month, climbing as the follicle develops and falling away after ovulation. A yearly sample records one day's position on that curve. What two yearly samples can expose is a change in ovarian output big enough to show through that variation, such as the fall at menopause. This is Do Health's monitoring schedule, not a general recommendation for everyone.