‡After 3 months, perform in accordance with guidelines for prostate cancer screening, depending on the age and race of the patient. Men using a testosterone gel should be advised by their healthcare provider on the ways of minimising the risk of testosterone transfer to women and children. Some studies have shown that insulin resistance may also improve following testosterone treatment (87,88). Testosterone pellets currently are the only long-acting testosterone treatment approved for use in the United States. This risk can be minimised by having patients wash their hands with soap and water after applying the gel, by covering the site of application with clothing after the gel has dried, and by washing the application site when skin-to-skin contact is expected. Primary hypogonadism requires no further investigation into the cause, although some clinicians do a karyotype to definitively diagnose or exclude Klinefelter syndrome. Klinefelter syndrome should be considered in adolescent males in whom puberty is delayed, young men with hypogonadism, and all adult men with very small testes and/or azoospermia (absent sperm in semen). Adult-onset testosterone deficiency has varied manifestations depending on the degree and duration of the deficiency. As adults, affected patients have poor muscle development, a high-pitched voice, a small scrotum, decreased phallic and testicular growth, sparse pubic and axillary hair, and an absence of body hair. Childhood-onset testosterone deficiency (see Male Hypogonadism in Children) is unrecognized until puberty is delayed. Second- or third-trimester onset of testosterone deficiency results in microphallus and undescended testes. Congenital hypogonadism of first-trimester onset results in inadequate male sexual differentiation (see also Sexual Differentiation, Adrenarche, and Puberty). Approximately 20–50% of HIV-infected men receiving highly active antiretroviral therapy are hypogonadal. In a case–control study of 40 cancer survivors it was found that 90% of those on opioid treatment were hypogonadal compared with only 40% of the control group (69). Various epidemiological studies in men have examined associations between testosterone and estradiol levels and BMD. There is an inverse linear relationship between total testosterone and BMI, and free testosterone concentrations also decrease with increasing BMI. Utilising data from the NHANES III survey, it was found that men in the lowest free testosterone tertile were four times as likely to have diabetes as those in the highest free testosterone tertile (47). Interestingly, low testosterone concentrations predict the development of type 2 diabetes. The concentrations of C-reactive protein in these patients are twice as high as those in eugonadal type 2 diabetics, whose C-reactive protein levels are already elevated compared with non-diabetics. The two basic types of hypogonadism are primary and secondary hypogonadism. Low testosterone (low T), also called male hypogonadism, may be caused by many things, such as aging, hormone changes, chemotherapy, and others. In 2019, a study was published that found that "enclomiphene has been shown to increase testosterone levels while stimulating follicular-stimulating hormone and luteinizing hormone production." It is therefore important that physicians are aware of the major symptoms of the condition and of the treatment options currently available. There is, however, no established consensus about what constitutes a significant rise in PSA levels or when urological referral should occur for men with normal PSA levels at baseline. It is not yet known if the normal PSA reference ranges should be lowered for men with type 2 diabetes. However, recent analysis has shown that, although there are case studies of occult conversions, these represent a very small number of the 200,000 cases of prostate cancer diagnosed in the United States and there is no evidence of causality. In addition, 5 alpha-reductase inhibitors, such as finasteride and dutasteride, reduce prostate volume and PSA levels. Case reports of occult cancers apparently stimulated to become clinically relevant cancers by testosterone treatment added to the concern. The origins of this concern date back to papers published in 1941 that reported that androgens stimulated prostate cancer, whereas oestrogen or castration reduced them (91).