Follicle-stimulating hormone

Fertility depends on a number of factors, with the functioning of the pituitary gland being the most essential of them. The pituitary gland produces hormones that influence fertility: luteinising hormone (LH) and follicle-stimulating hormone (FSH).

FSH is a protein that regulates a woman’s menstrual cycle through the growth and maturing of ovarian follicles. In men, the same hormone affects the production of sperm.

In the first phase of a woman’s menstrual cycle, known as the follicular phase, FSH causes female hormone oestradiol synthesis in the follicle, which thickens the uterus lining. In the next phase, the luteal phase, FSH promotes the secretion of progesterone. Oestradiol and progesterone assist the pituitary gland in controlling the level of FSH.

When the follicle is mature, it bursts, and the egg is released from the follicle, meaning that ovulation happens. Ovulation is influenced by a sudden increase in the luteinising hormone, LH (“luteus” is Latin for yellow). LH also supports the production and secretion of progesterone. If the egg is not fertilised, the corpus luteum decays and the menstrual period begins. During menopause, the ovaries stop functioning and FSH concentration increases.

When should FSH be measured?

Measuring FSH levels can help in investigating infertility, irregular menstrual periods, and pituitary gland disorders. In children, FSH and LH levels are examined for diagnosing delayed or early puberty and examining growth problems.

If a man has a low sperm count, FSH levels are measured to find out the reason.

In women, FSH and LH levels can be of use in discerning between primary ovarian insufficiency (ovarian insufficiency because of the ovaries) and secondary ovarian insufficiency (ovarian insufficiency due to the pituitary gland or disorders of the pituitary gland).

FSH may need to be measured when examining the causes of the following symptoms:

• Disturbance of the menstrual cycle
• Night sweats
• Sleep disorder
• Mental disorder
• Loss of libido
• Vaginal dryness
• Infertility
• Determining the time of ovulation
• Testosterone deficiency in men (hypogonadism, a condition caused by diminished production of sex hormones)

What does the FSH test measure?

The test indicates the level of FSH in the blood. The test is often taken when examining the cause of infertility or examining the functioning of the pituitary gland.