Estradiol and follicle stimulating hormone (FSH) are connected because they are both hormones that control the reproductive system. FSH and estradiol are found in both men and women. While FSH is produced by the pituitary gland, estradiol is secreted from the ovaries in women and the testicles in men. Doctors may measure levels of FSH and estradiol in the blood to investigate fertility problems in both sexes.
Both FSH and estradiol blood levels may be tested when doctors are investigating the cause of irregular menstrual periods in women. FSH is often tested along with another hormone known as luteinizing hormone (LH). LH and FSH are made by cells called gonadotrophs, which are found inside the pituitary gland.
In women, FSH acts on the ovaries causing maturation of the follicles, or egg containers. LH stimulates the release of eggs from the mature follicles. Once the eggs have been released, some cells in the follicles go on to produce estradiol.
High levels of estradiol in the blood are detected by the brain and this causes a reduction of LH and FSH production. In this way, FSH and estradiol take part in a regulatory system known as a negative feedback loop, which works in a way that resembles a heating thermostat. This system enables the body to adapt to changing situations and regulate hormone levels accordingly. Estradiol is one of the hormones used in contraceptive pills, as increasing its levels in the body leads to a reduction in LH and FSH. The reduction in FSH and LH means that the ovaries are not stimulated to mature and release eggs, which prevents conception from occurring.
Due to the negative feedback effect, levels of FSH and estradiol do not normally rise or fall together. High blood estradiol would be expected to suppress LH and FSH production, while low estradiol levels would be associated with increasing FSH and LH. Raised FSH and LH levels in children may indicate abnormally early puberty, which could be caused by a tumor in the ovaries or testicles or a tumor elsewhere that is producing hormones. Doctors approach treatment in different ways depending on the cause of the problem.
In adults, high levels of FSH and LH can indicate that the ovaries or testicles are not functioning, leading to a decreased production of estradiol and testosterone. Problems such as injury, radiation damage, infection and other diseases can cause ovaries and testicles to fail. Treatment varies according to the underlying cause.