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What is FSH? Everything you need to know about the hormone

Updated: Mar 27, 2023

Follicle-stimulating hormone (FSH) plays an important role in the reproductive functions of both women and men. It is produced in the anterior lobe of the pituitary gland under the control of the hypothalamus. This hormone affects certain cells in the ovaries and testicles.

In women, FSH together with luteinizing hormone (LH) stimulate the growth and maturation of follicles in the ovaries. In men, FSH acts on the cells in the testicles that are responsible for producing sperm.

How does the FSH level change?

In some cases, the level of follicle-stimulating hormone can be too high or too low. The most common symptoms of this include irregular or absent periods, low sperm count, and infertility.

The FSH level in men is relatively low and stable and does not fluctuate after puberty. However, in the different phases of the menstrual cycle in women, the level of FSH varies in relation to other reproductive hormones. During menopause, the concentration of FSH rises due to changes in the function of the ovaries and the decreased level of estrogen.

When is it advisable to test your FSH level?

There are various reasons why someone may decide to check the level of FSH in their body. For women, irregular or absent menstruation, inability to conceive, signs of menopause, or other unusual symptoms related to the function of the pituitary gland may be sufficient reasons for an FSH test.

The MENO-Check® test can quickly and easily detect if the concentration of FSH in the blood exceeds 25 mIU/mL, which would confirm menopause in women. If the test is negative and you are still experiencing symptoms of menopause, it is recommended to consult a doctor.

Other causes of high or low FSH

A high level of FSH in the blood combined with low levels of sex hormones could point to a condition called primary (hypergonadotropic) hypogonadism. In certain cases, the gonads cannot produce enough sex hormones. The body then communicates to the hypothalamus and pituitary gland that more FSH and LH are needed to normalise sex hormone levels. As a result, the level of follicle-stimulating hormone rises above the normal limits.

The opposite condition – low level of FSH in the blood and low levels of sex hormones, is called secondary (hypogonadotropic) hypogonadism. In individuals with secondary hypogonadism, the pituitary gland does not produce the required amounts of FSH and LH. Because of this, estradiol and inhibin levels are low in women and follicle maturation is impaired.

Another common cause of elevated FSH is primary ovarian insufficiency (POI). In this case, the ovaries stop functioning normally earlier than usual.

Pituitary adenomas are among the rarer causes of high FSH. Pituitary adenomas are benign, noncancerous, and do not spread to other parts of the body.

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