The likelihood of sarcopenia (age-related muscle loss) and diminished muscle strength rises as testosterone levels naturally fall with age; however, research indicates that testosterone therapy may mitigate these effects in older men, enhancing physical performance, sexual drive, and muscle mass . This MR study suggests that muscle mass itself may not be related to testosterone; however, the effect of fat mass can lower testosterone levels. Therefore, this MR study suggests that fat mass lowers testosterone levels, while muscle mass may not be related to testosterone levels. Βcoefficients with 95% CIs of weighted median for the effect of one unit increase in fat mass, fat-free mass, and body mass index (BMI) on testosterone levels (total testosterone, bioavailable testosterone, and sex hormone-binding globulin) in men. The participant advisory board has read and commented on the study material and will be contacted for continuous sparring. The participant advisory board meetings were arranged prior to application for ethical approval of the study to secure inputs in terms of relevance of research questions, recruitment, outcomes and participant time consumption. During legal transitioning individuals may change CPR and data from the two CPR numbers is merged. All individuals in Denmark have a civil registration number (CPR) reflecting binary gender. The participants accept study participation by written informed consent. The participants will spend 1 day in BIC per visit and all examinations use the same equipment and study protocols (table 1). The study is a prospective single-centre observational cohort study at Body Identity Clinic (BIC), Odense University Hospital, Odense, Denmark of 10 years duration. The locker room at the local gym is unlikely to be monitored by a qualified medical professional. If you performed a quick online search for "prevention of gynecomastia," nearly all articles are concerned with PED (performance enhancing drugs) used for bodybuilding or enhancing sports performance. Unsupervised (or poorly supervised) use of testosterone is certainly reckless and can result in gynecomastia. That has lead to the term "testosterone-induced gynecomastia." That means excess testosterone can become excess estrogen, which can cause or contribute to a hormonal imbalance, in turn leading to enlarged breast tissue. Although, frankly, in a review that I wrote in the New England Journal of Medicine where we reviewed as much of this as we could, we found no cases of stroke or severe clotting related to testosterone therapy. If you’re taking supplemental testosterone without proper supervision or precautions, the risks of high blood pressure can definitely increase. The true issue at hand is how testosterone affects the thickness of blood. In this study, body composition (fat mass, fat-free mass, and body mass index BMI) in men was used as exposure variables, and IVs were defined using genome-wide association study (GWAS) data from the UK Biobank (18). Nevertheless, the association between fat or muscle distribution and testosterone levels is not yet known. Insufficient testosterone levels can lead to various signs and symptoms that may impact a males’ physical well-being and masculinity (1). When comparing the causal effect on testosterone levels, there was a consistent trend that the effect of fat mass was more potent than that of fat-free mass. We have previously used this design in women with polycystic ovary syndrome.46 The gold-standard research design to assess benefits and risks of testosterone therapy in transgender persons is a long-term placebo-controlled randomised trial on masculinising therapy, however, it is deeply unethical to perform such a study, when gender dysphoria is present. Masculinising testosterone treatment in transgender men is for life and currently no prospective data are available on long-term morbidity. A retrospective study in transgender men reported no cases of myocardial infarction after 10 years of testosterone treatment,16 but the retrospective study design increased risk of selection bias due to lost to follow-up before 10 years. The real question should be, "Will my body recognize and react to the FDA-approved medication that you prescribe in the same way it would react to naturally occurring hormones? The fact is, testosterone injections, topicals (gels/creams), and pellet implants all utilize an FDA-approved formula that is not "bioidentical" — "bioidentical" is something of a hormone myth. What are bioidentical hormones doing that FDA-approved testosterone isn’t? "Bioidentical" testosterone has been marketed as somehow better, safer, more effective, better absorbed by the body, and so on, by using excellent marketing phrases like "natural, non-chemical, and pure." The idea was simple — create a time-release testosterone product and implant it in the body. Finally, there are hardened testosterone pellets that are implanted under the skin, intended to stay in your body for 4–6 months. Also, we know that oral forms of testosterone can have harmful effects on the liver. Testosterone therapy has modest advantages, especially for men who have hypogonadism symptoms and low testosterone levels. Testosterone therapy may make sense for women who have low testosterone levels and symptoms that might be due to testosterone deficiency. This may occur because gender-affirming treatments seem effective in reducing gender dysphoria and improving overall well-being in transgender people, which can have positive effects on relationships with family members and other social connections 20,21,28,29.