Metabolic syndrome is characterized by central obesity, dyslipidemia, hypertension, and insulin resistance. Each lifestyle disease and also metabolic syndrome are closely associated with decreased serum testosterone. In general, it is believed that testosterone is inversely related to adiponectine level, which is thought to be a key molecule in the etiology of metabolic syndrome. However, no inverse correlation exists between them in patients with LOH. Testosterone replacement treatment is expected to be one of treatments for metabolic syndrome.