Causes of Hypogonadism
Testosterone deficiency (hypogonadism) may be present at birth (congenital) or may develop later (acquired).
Testosterone deficiency is classified by the location of its cause along the hypothalamic-pituitary-gonadal axis:
- Primary, disruption in the testicles
- Secondary, disruption in the pituitary
- Tertiary, disruption in the hypothalamus
The most common congenital cause is Klinefelter's syndrome. This condition, which is caused by an extra X chromosome, results in infertility, sparse facial and body hair, abnormal breast enlargement (gynecomastia), and small testes.
Congenital hormonal disorders such as leutenizing hormone-releasing hormone (LHRH) deficiency and gonadotropin-releasing hormone (GnRH) deficiency (e.g., Kallmann's syndrome) also may cause testosterone deficiency.
Other congenital causes include absence of the testes (anorchism; also may be acquired) and failure of the testicles to descend into the scrotum (cryptorchidism).
Acquired causes of testosterone deficiency include the following:
- Chemotherapy
- Damage occurring during surgery involving the pituitary gland, hypothalamus, or testes
- Glandular malformation
- Head trauma that affects the hypothalamus
- Infection (e.g., meningitis, syphilis, mumps)
- Isolated LH deficiency (e.g., fertile eunuch syndrome)
- Radiation therapy
- Testicular trauma
- Tumors of the pituitary gland, hypothalamus, or testicles
Studies have shown that men with obesity, diabetes, or hypertension may be twice as likely to have low testosterone levels.
