Follicle stimulating hormone (FSH)
Why this test?
To identify the causes of infertility (along with tests for other sex hormones: luteinizing, testosterone, estradiol, progesterone).
To determine the phase of the menstrual cycle (menopause).
To diagnose the causes of spermatogenesis disorders, a reduced number of spermatozoa.
To identify primary or secondary causes of sexual dysfunctions (pathology of the gonads or hypothalamic-pituitary disorders).
For the diagnosis of early or late sexual development. To monitor the effectiveness of hormone therapy.
In what cases is it prescribed?
With infertility. If pituitary pathology and sexual dysfunction are suspected.
When the menstrual cycle is disturbed (its absence or irregularity).
When the patient has congenital diseases with chromosomal abnormalities.
With disorders of growth and maturation in children.
When using hormonal drugs.
Follicle-stimulating hormone (FSH) together with luteinizing hormone (LH) is produced in the anterior lobe of the pituitary gland under the influence of hypothalamic gonadotropin-releasing hormone. Secretion of FSH occurs in pulse mode with intervals of 1-4 hours. During an emission lasting about 15 minutes, the concentration of FSH exceeds the average indicator by 1.5-2.5 times and is regulated by the level of sex hormones according to the principle of negative feedback. Low levels of sex hormones stimulate the release of FSH into the blood, and high levels suppress it. The protein inhibin B, which is synthesized in ovarian cells in women and cells lining the seminiferous tubules (Sertoli cells) in men, also suppresses FSH production. In children, the level of FSH increases for a short time after birth and falls sharply at 6 months for boys and at 1-2 years for girls. Then it increases before the onset of puberty and the appearance of secondary sexual characteristics.
One of the first laboratory indicators of the beginning of the period of puberty (sexual maturation) in children is an increase in the concentration of FSH at night. At the same time, the response of the gonads increases and the level of sex hormones increases. In women, FSH stimulates the maturation of ovarian follicles, prepares them for the action of luteinizing hormone and enhances the release of estrogens. The menstrual cycle consists of follicular and luteal phases. The first phase of the cycle takes place under the influence of FSH: the follicle increases and produces estradiol, and at the end, a sharp increase in the levels of follicle-stimulating and luteinizing hormones provokes ovulation - the rupture of a mature follicle and the release of an egg. Then comes the luteal phase, during which FSH promotes the production of progesterone.
Estradiol and progesterone regulate FSH synthesis by the pituitary gland in a feedback loop. During menopause, the ovaries stop functioning and the reduced secretion of estradiol leads to increased concentrations of follicle-stimulating and luteinizing hormones. In men, FSH affects the development of seminiferous tubules, increases the concentration of testosterone, stimulates the formation and maturation of sperm in the testicles, and promotes the production of androgen-binding protein. After puberty, the level of FSH in men is relatively constant.
Primary testicular insufficiency leads to an increase in its number. Analysis of gonadotropic hormones allows you to determine the level of hormonal regulation disorders - primary (dependent on the gonads themselves) or secondary (related to the hypothalamic-pituitary axis). In patients with testicular (or ovarian) dysfunction, low levels of FSH indicate dysfunction of the hypothalamus or pituitary gland. An increase in FSH indicates a primary pathology of the gonads. Simultaneous tests for follicle-stimulating and luteinizing hormones are used to diagnose male and female infertility and determine treatment tactics.