As men age, testosterone levels gradually begin to decline. Low testosterone levels in men - male hypogonadism or testosterone deficiency syndrome - can lead to a range of negative health consequences, such as decreased sexual function, depression, and decreased muscle and bone mass. Earlier work has shown that about a third of men with type 2 diabetes have hypogonadism. Based on these results, the authors of a new study decided to test whether testosterone therapy could reduce the risk of diabetes in the future. Published in The Lancet Diabetes & Endocrinology, it is considered the largest study ever conducted on the subject. The experiment involved more than 1000 men aged 50 to 74 years with overweight or obesity - the main factors in the development of diabetes. The subjects were divided into two groups: one received testosterone injections every three months, and the other received a placebo. In addition, they all gained access to the WW lifestyle weight loss program, in which 30% of men from both groups attended meetings and 70% achieved the recommended amount of exercise for weight loss. Over the two years of the study, participants in both groups lost an average of about 4 kg of weight. The most common adverse side effect of testosterone therapy was an increase in red blood cell count. In 22% of men, this increased blood clotting, which increases the risk of developing blood clots. After two years, 21% of men in the placebo group developed type 2 diabetes, while in the group of subjects receiving testosterone therapy, this figure was only 12%. The second group also showed a stronger decrease in blood sugar when measured on an empty stomach, a slight improvement in sexual function, and an increase in muscle mass.