The term amenorrhea means absence of menstrual bleeding. It is a normal condition in postmenopausal, pregnant and lactating women, and also in prepubescent girls. Absence of menses in women of childbearing age requires the first exclusion of pregnancy. With a negative result of a pregnancy test, it is necessary to actively look for other reasons causing disturbances in the menstrual cycle. There are two types of amenorrhea – primary and secondary. Primary amenorrhea is the absence of menstruation before the age of 16, with normal growth and prominent secondary genital markings. If these are absent by the age of 13 and menarche (first menstruation) has not occurred, it is recommended to carry out research in order to find the reasons for this. Most often, primary amenorrhea is associated with genetic or anatomical abnormalities. According to their frequency, they are arranged as follows: Chromosomal abnormalities leading to gonadal dysgenesis (Turner’s syndrome) – 45%; Physiologically delayed puberty (in athletes or very low weight girls) – 20%; Müllerian agenesis (congenital malformation affecting the development of the Müllerian duct in the female fetus, which will give rise to the female reproductive system and as a result – missing uterus, cervix and/or vagina) – 15%. Secondary amenorrhea is the cessation of menstruation in women with menarche. Oligomenorrhea is a term used for a menstrual cycle lasting more than 35 days. Menstrual cycle is not the period of bleeding (menstruation), but the interval from one monthly bleeding to the beginning of the next monthly bleeding. So far, there is no clear boundary between oligomenorrhea and amenorrhea. According to some authors, it is 6 months, but in practice more often the delay of menstruation by more than 90 days is defined as amenorrhea. The causes of secondary amenorrhea can be: Ovarian – 40%; Hypothalamic – 35%; Pituitary – 19%; Uterine – 5% and others. Among the ovarian causes with the greatest frequency is polycystic ovary syndrome. Women with this disease have disorders in the metabolism of androgens and estrogens, as well as in the control of androgen production. There are many reasons for this disease, such as dysregulation of the hypothalamus-pituitary-ovary axis, obesity and the resulting hyperinsulinemia and insulin resistance. As a result, oligo-/amenorrhea, hyperandrogenemia and characteristic ultrasound changes in the ovaries develop. The presence of 2 of the 3 listed criteria establishes the diagnosis. Premature ovarian failure (PON) is a syndrome characterized by the loss of ovarian function before the age of 40. It is characterized by amenorrhea, reduced estrogen levels and increased follicle-stimulating hormone. The condition resembles menopause, but with premature ovarian failure, spontaneous ovarian activity and even pregnancy are possible. NEWS_MORE_BOX Of the pituitary causes, the most common is hyperprolactinemia. It may be the result of a pituitary adenoma secreting excessive amounts of prolactin – a prolactinoma,drug-induced or due to metabolic disorders (severe hypothyroidism, chronic renal failure or severe liver disease). Prolactin changes the sensitivity of the ovaries to gonadotropins (follicle-stimulating and luteinizing hormone), so-called “ovarian resistance” to them, which reduces the synthesis of estrogens and progesterone, and the consequence is oligo-/amenorrhea. Hypopituitarism is a condition of partial or complete deficiency of hormones synthesized by the pituitary gland. In processes that disrupt its function, the cells secreting gonadotropic hormones are the first to suffer. Decreased or absent stimulation by follicle-stimulating and luteinizing hormone may also be the cause of a lack of menstruation. Rapid weight loss may have a negative effect on the releasing hormones secreted by the hypothalamus, thereby suppressing hormone synthesis along the entire gonadal axis. Other causes of impaired function of the hypothalamus are various inflammatory or tumor processes in it. Intrauterine adhesions (Asherman’s syndrome) are a common cause of mechanically induced amenorrhea. Women affected by this disease should seek gynecological help.