Men's Health Knowledge Centre
Hypogonadism
Etiology
Male hypogonadism is characterized by a deficiency of endogenous testosterone production resulting in abnormally low levels of circulating testosterone. Hypogonadism can be caused by a number of disorders, the most frequently observed being idiopathic hypogonadotrophic hypogonadism, hypopituitarism, Klinefelter’s syndrome or late-onset hypogonadism.
Figure 1. Classification of hypogonadism.2
The idiopathic hypogonadotrophic hypogonadism is a constitutional disorder of GnRH secretion. Hypopituitarism may occur as a result of various diseases of the pituitary gland, e.g. adenoma or ischemia, as a consequence of radio-therapy, drug abuse, medications like cytostatics, cardiac drugs, diuretics and antihypertensives, or post-op Klinefelter’s syndrome is a congenital aberration of the number of chromosomes. The condition is caused by one or more extra X-chromosomes. The signs of Klinefelter’s syndrome are almost unnoticeable in childhood. Occasionally, boys affected with the condition are referred for hypoplasia of the external genitalia or extra-long legs.
Many systemic diseases (e.g. diabetes mellitus, generalized infections, metabolic syndrome) correlate with low testosterone levels.1 Therefore, hypogonadism as an early sign can contribute to an early diagnosis of the underlying condition. Another cause for male hypogonadism is the naturally occurring, age-related decrease of testosterone serum levels which may lead to a state of androgen deficiency.
Figure 2. Prevalence of low levels of total and bioavailable testosterone as an index of male hypogonadism according to decade of life3. Dark bars represent the percentage of population with total testosterone levels below 11.3 nmol/L (325 ng/dl), and light bars represent the percentage of the population with bioavailable testosterone levels under 70ng per deciliter.
References
1. Jockenhövel F: Male Hypogonadism. UNI-MED Verlag Bremen 2004.
2. Schering AG: Classification of hypogonadism and selected syndroms. www.get-back-on-track.com/en/professionals/00_meta/07_praesentationen/p_con_0007_01_02.php, accessed on 28 th July 2004
3. Rhoden EL, Morgentaler A: Risks of testosterone-replacement therapy and recommendations for monitoring. N Engl J Med 2004; 350: 482–492.