BackgroundChronic obstructive pulmonary disease (COPD) is now considered a systemic disease that affects organs beyond the lungs and airways. The endocrine functions, primarily the gonads, are affected in COPD. PurposeTo assess late-onset hypogonadism (LOH) among male patients with COPD. Materials and methodsThis case-control study included 90 male patients with different degrees of COPD and another 90 age-matched and sex-matched control participants with normal pulmonary function that were subjected to assessment of symptoms of hypogonadism and measurement of free and total testosterone, follicle stimulating hormone (FSH), luteinizing hormone (LH), and dehydroepiandrosterone-sulfate (DHEAS). ResultsSerum levels of FSH, LH, DHEAS, total, and free testosterone of patients with mild COPD were nonsignificantly different from those of controls. In moderate disease, only DHEAS was significantly lower in comparison with the controls. Patients with severe COPD had significantly lower FSH and total testosterone levels in comparison with the controls. There was a positive correlation between pulmonary function tests and serum levels of sex hormones. There was a significant relation between the severity of COPD and total and free testosterone, DHEAS, and FSH levels, with the lowest levels of hormones in the severe grade. Twenty-five percent of patients with COPD fulfilled the diagnostic criteria of LOH versus 10% in their age-matched controls. Conclusion LOH is more common in men with COPD and occurs at a younger age than their matched controls with normal pulmonary functions. The severity of the disease leads to increased incidence of LOH. Therefore, screening for hypogonadism in patients with severe COPD is recommended.