Low levels of FSH

Follicle-stimulating hormone (FSH) is one of the gonadotropins, a key hormone involved in the reproductive function and crucial for the woman’s fertility. Of note, as one of the gonadotropins, the FSH is involved in the process of the development of the reproductive system, period of puberty and the development of secondary sex characteristics. Various conditions and disorders affect FSH production.

Smiling gynecologist is sitting beside table. She holding clipboard with scheme of reproductive system to coupleReference values

Women

  • Age 0-7 years: <6.7 mIU/mL;
  • Age 8 years to adult:
  • Follicular phase: 3.1-7.9 mIU/mL;
  • Ovulation peak: 2.3-18.5 mIU/mL;
  • Luteal phase: 1.4-5.5 mIU/mL;
  • Postmenopausal: 30.6-106.3 mIU/mL;

Men

  • Age 0-7 years: <6.7 mIU/mL;
  • Age 8 years-adult:1.3-19.3 mIU/mL;

Various congenital and acquired disorders affect the production of GnRH, FSH and LH.

Gonads neoplasms

Ovarian tumors, neoplasms of the testes or adrenal glands produce estrogen or androgens and, in turn, inhibit the production of FSH.

Polycystic ovarian syndrome

Polycystic ovarian syndrome is a complex of symptoms caused by excessive androgen levels in females. Hormonal changes cause the development of hirsutism (excessive hair growth on the chin, chest, and spine), acne, menstrual abnormalities (including absence or infrequent periods, heavy menstruations, etc.) and infertility.

Kallmann syndrome

Kallmann syndrome is a congenital disorder affecting both genders caused by genetic mutations which result in gonadotropin-releasing hormone (GnRH) deficiency (hypogondotropic hypogonadism), low LH and FSH levels, and, respectively, delayed or absent puberty and impaired or absent sense of smell. Individuals with Kallman syndrome are infertile. Usually, the diagnosis is made during the teenage years when a child fails to develop puberty and distinct sexual characteristics. However, the disease may be suspected earlier, for example, in infant boys with undescended testicles or small penis. If treated these persons may restore their fertility and develop normally. Nevertheless, treated or not the disease itself is not life-threatening.

Hypothalamic suppression

Hypothalamic suppression (hypothalamic hypogonadism) is a condition characterized by the insufficient secretion of gonadotropin-releasing hormone by the hypothalamus and, as a result, decreased values of FSH and LH and sex hormones.

Hyperprolactinemia

Hyperprolactinemia is considered the most common disorder of the pituitary gland characterized by the increased levels of serum prolactin (PRL>20 ng/mL) in the absence of pregnancy or lactation. Some medications when administered for a long period of time influence the production of prolactin and may cause hyperprolactinemia. Nevertheless, prolactin-secreting tumors are the most common reason for this condition. Increased prolactin levels impair person’s fertility, influence the functioning of the reproductive system and promote the production of milk in the absence of nursing.

Gonadotropin deficiency

Any disorder of the hypothalamic-pituitary axis and insufficient secretion of FSH and LH leads to the development of the hypogonadotropic hypogonadism (secondary hypogonadism), which results in the poor stimulation of the ovaries with gonadotropins, delayed sexual development and impaired development of the ovarian follicles and disorders of the menstrual cycle in women or impaired spermatogenesis in men.

Anorexia nervosa

Anorexia nervosa is an eating disorder in which a person restricts food intake due to the fear of gaining weight. The behavioral pattern in anorexia leads to severe malnutrition which damages the whole body. Pulsatile excretion of gonadotropin-releasing hormone is also impaired and, therefore, FSH and LH levels are decreased.

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