12th April 2024

Secondary hypogonadism (hypogonadotropic hypogonadism)

Secondary hypogonadism occurs when there is a dysfunction in the hypothalamus or pituitary gland, leading to the inability to produce gonadotrophins (LH & FSH). It can also be caused by the suppression of the hypothalamus by high prolactin or thyroid hormone levels. Acquired causes may be due to radiotherapy/chemotherapy or trauma. Congenital causes include Kallman Syndrome and panhypopituitarism. Other causes include chronic illness, excess exercise, malnutrition, obesity, and stress, which may also lead to the dysfunction of the hypothalamus or pituitary gland.

Kallman syndrome

Kallman syndrome is a result of the failure of the migration of GnRH-secreting neurons from the olfactory epithelium to the hypothalamus during embryogenesis. This defect also leads to hyposmia or anosmia. This leads to a reduced level of GnRH and, in turn, reduced levels of gonadotrophins (LH & FSH) and sex hormones – testosterone in males and oestrogen and progesterone in females. This leads to delayed puberty or failure to complete puberty. Both underdeveloped primary and secondary sex characteristics are listed below.

Both males and females are infertile. Male patients are found with small testes (<4mL), decreased muscle mass and delayed growth spurt. Females present with a lack of breast development, delayed growth spurt, lack of pubic hair growth and primary menorrhoea.

Kallman syndrome can be diagnosed by overall reduced levels of GnRH, gonadotropins (LH& FSH), testosterone/ oestrogen and progesterone. The main treatment is hormone replacement to promote puberty and the development of secondary sexual characteristics. As these individuals are also at risk of osteopenia and osteoporosis, calcium and vitamin D supplements are also part of the management.