Etiology Of Hypogonadism

Late Onset Hypogonadism

Late-onset hypogonadism is associated with advancing age and characterized by low testosterone levels (below the young healthy adult male reference range) and symptoms.1 Some decline in testosterone level is normal as men age, due to reduced function of the testes and the hypothalamic-pituitary system (Figure 3). Therefore, LOH is a mixture between primary and secondary hypogonadism. However, late-onset hypogonadism may lead to a significant decline in the quality of life and may adversely impact various organ systems. About 34% of men aged between 45 and 54 years have total testosterone levels below the physiological range for younger men, reaching 40% in men aged 55 to 74 years, 45.5% in men aged 75 to 84 years and 50.0% in men aged 85 years or older.2

Figure 3. Age-related Decline in Testicular Function
Age Related Decline

Additionally, target organ resistance (androgen resistance) is a rare form of hypogonadism, usually resulting from a genetic defect of the androgen receptor. Despite high testosterone levels, the target organs cannot respond to available testosterone.
The classification of hypogonadism is summarized in the (Figure 4).

Figure 4.
Classification of Hypogonadism

Regardless of the underlying cause of hypogonadism, the treatment approach is aimed at returning testosterone to physiologically normal levels.

1. Wang, C., E. Nieschlag, R. Swerdloff, et al. Investigation, treatment and monitoring of late-onset hypogonadism in males: ISA, ISSAM, EAU, EAA and ASA recommendations. Eur J Endocrinol 2008, 159(5): 507-514.
2. Mulligan T, Frick MF, Zuraw QC, et al. Prevalence of hypogonadism in males aged at least 45 years: the HIM study. Int J Clin Pract 2006; 60(7): 762-9.