In addition, Vikan et al showed that the risk of developing T2DM decreased significantly with increasing levels of total testosterone. However, no statistically significant association was noted between the levels of bioavailable testosterone and the development of T2DM in this study. A list of studies that analyzed the association between testosterone level and mortality is presented in Table 3. CAD indicates coronary artery disease; CCS, case–control study; FAI, free androgen index; FT, free testosterone; TT, total testosterone. TRT is used to bring testosterone levels back to normal and improve symptoms like fatigue, low sex drive, and depression. Testosterone Replacement Therapy (TRT) is a medical treatment used to help men with low testosterone levels. Until the results of such large‐scale studies become available, we recommend caution when administering testosterone to elderly men. Haddad et al defined adverse cardiovascular events as cardiovascular death, fatal and nonfatal myocardial infarction, angina, arrhythmia, revascularization procedures, and stroke. The effects of testosterone replacement on different lipoprotein subfractions have been reported in a previous section of this review article. Haddad et al performed a meta‐analysis of 30 placebo‐controlled randomized trials, which included 808 men in the testosterone replacement group and 834 men in the placebo group.31 The authors found no changes in systolic or diastolic blood pressure with testosterone replacement. When all the above‐mentioned cardiovascular events were pooled, Calof et al still did not find a statistically significant difference between the 2 groups. Finally, we summarize the effects of testosterone replacement therapy on cardiovascular disease and its risk factors and major adverse cardiovascular events. An increased risk of premature cardiovascular events in men initially led to the belief that testosterone had detrimental effects on cardiovascular health. By optimizing testosterone levels, men can potentially improve their heart health and reduce the risk of cardiovascular diseases. This review article has demonstrated that normal testosterone levels play an important role in maintaining cardiovascular health, and testosterone replacement therapy in men with hypogonadism improves obesity, T2DM, myocardial ischemia, exercise capacity, and QTc length. Although the results of the 3 meta‐analyses seem to indicate that testosterone replacement therapy does not cause an increase in the rate of adverse cardiovascular events,31,146–147 a study published by Basaria et al in 2010 reported contradictory results. Charbit et al provided neither baseline testosterone levels nor QTc length.115 Pecori Giraldi et al in their analysis of 26 men with hypogonadism demonstrated that testosterone replacement therapy caused normalization of the QTc interval in all the subjects who were found to have prolonged QTc.117 The average QTc interval shortening in Pecori Giraldi's study was 66 ms. All patients received intramuscular testosterone except 1, who was on a testosterone transdermal patch. Moreover, epidemiologic studies have shown that men are at higher risk of having unfavorable lipid profiles80 and suffer from cardiovascular disease mortality more frequently when compared with women.81–82 These observations have prompted some investigators to hypothesize that the difference in incident dyslipidemia and cardiovascular disease between the 2 sexes is related to the different levels of circulating sex hormones. When the body doesn’t produce enough testosterone, doctors may recommend TRT to help bring hormone levels back to normal. As the use of TRT continues to grow, knowing its effects on heart health will help people make better decisions. It also goes over how common fast heart rate is as a side effect, which people may be at higher risk, and when to talk to a doctor. It can cause the body to keep more sodium, which can increase blood volume. But in older adults or people with heart conditions, a faster resting heart rate can be a concern. This higher energy use can raise the resting heart rate in some people. People with anxiety, sleep disorders, or high blood pressure may feel these effects more strongly. The autonomic nervous system controls automatic functions in the body, such as heart rate and breathing. When there are more red blood cells, the blood becomes thicker. It also impacts how blood vessels expand and contract, which affects blood pressure. Blood tests must confirm low levels, and symptoms must be present. It is only approved for people with clear medical reasons for low testosterone. The choice depends on a person’s health, preferences, lifestyle, and medical history. Each method delivers testosterone into the body in a different way. While some decline in testosterone is normal with age, some men experience drops that cause symptoms and require treatment. Testosterone is a vital hormone that plays a crucial role in men’s overall health and well-being. Similar to the previous reports, TRT resulted in a significant increase in hemoglobin levels.36 They concluded that TRT for hypogonadism does not appear to increase PSA or the risk of prostate cancer. All four studies included in this meta-analysis evaluated the effects of TRT on LVEF as well. A number of studies have examined the association between testosterone levels and carotid IMT, with all the studies showing an inverse correlation between these 2 variables.126–128,32,129–132 The results of these studies are summarized in Table 7. In a study of 11 nonobese men with hypogonadism, Charbit et al evaluated the effects of a single intramuscular injection of testosterone enanthate 250 mg on heart rate–independent QT interval length.115 The authors measured QT length at 3 points after the administration of testosterone. Likewise, no conclusion can be made regarding the association between testosterone replacement therapy and its effect on CRP levels. These effects have been shown in vitro and include increased lipolysis and decreased fat accumulation in visceral adipose tissue.25,27,64,73–76 It is reasonable to assume that testosterone causes improvement in glycemic control at least in part because of its positive effects on visceral adiposity. Still, other authors have investigated the risk of developing T2DM in the setting of low testosterone levels from a different perspective. Vikan et al reported similar findings for the association between free testosterone levels and the development of T2DM.