Normal gonadal development and maintenance of function depend on the integrity of the hypothalamic-pituitary-gonadal axis. Abnormalities in any part of this axis can lead to a lack of gonadal secretion, i.e. hypogonadism. Depending on the etiology and biochemical changes, hypogonadism can be divided into two categories: hypergonadotropic hypogonadism and hypogonadotropic hypogonadism (HH). Hypogonadotropic hypogonadism: It is a decrease in the secretion of sex hormones due to abnormal development of the gonads themselves (testes/ovaries) or diseases of various causes, and is characterized by a decrease in gonadotropins and a feedback increase in pituitary gonadotropins (LH and FSH). Hypogonadotropic hypogonadism: It is a group of diseases caused by decreased gonadal function and decreased secretion of sex hormones due to the lack or decrease of hypothalamic gonadotropin-releasing hormone (GnRH) or pituitary LH and FSH secretion, and the biochemical manifestations are decreased sex hormones and gonadotropins. Hypogonadism results in a decrease in the synthesis of sex hormones and is characterized by degeneration of secondary sexual characteristics, hypogonadism, amenorrhea (in females) and/or infertility in adults, and delayed or absent puberty in children with prepubertal onset. The etiology and epidemiology of hypogonadism are complex, and the causes are not significantly different in adolescents than in adults, but can be broadly classified into two categories: congenital and acquired. The most common causes of hypergonadotropic hypogonadism in male and female adolescents are Klinefelter’s syndrome and Turner’s syndrome, respectively, as well as some rare genetic defects and acquired gonadal impairment.