The title says it all, as the study is quite clear. DHT “…was most consistently associated with a lower level of insulin resistance and lower risk of incident diabetes” in the words of the study’s lead author. The current darling of “aging/obese male” treatments – testosterone (T) – was not associated with lower insulin resistance and diabetes risk. The steroid carrier SHBG was also linked to lower risk but the relationship did not hold across all tests done, thus leaving only DHT as the likely metabolically beneficial steroid in males (at least in this study). The study authors think that their results can explain the contradictory results from other studies in regards to T and its role in diabesity. Some studies found protective, others negative, and still others null effects of T in this cluster of metabolic conditions. The authors think that measuring T does little good since DHT is the likely protective factor and studies assessing the role of androgens in diabesity should measure at least DHT or DHT and it precursor T, but never T only.
“…“Among testosterone, [sex-hormone binding globulin] and dihydrotestosterone, we found that [dihydrotestosterone] was most consistently associated with a lower level of insulin resistance and lower risk of incident diabetes in older men,” Kenneth J. Mukamal, MD, MPH, of Beth Israel Deaconess Medical Center in Boston, told Endocrine Today. Mukamal and colleagues evaluated data from the Cardiovascular Health Study on 852 men free of diabetes and cardiovascular disease in 1994 to determine the relationships between sex hormones, insulin resistance and incident diabetes. Homeostasis model of assessment for insulin resistance (HOMA-IR) was used to estimate insulin resistance, and the Gutt index was used to estimate insulin sensitivity. Follow-up was conducted for a mean of 9.8 years. After adjustment for demographics, alcohol consumption, smoking status and BMI, SHBG and dihydrotestosterone were inversely associated with HOMA-IR (P = .01 for both). Better insulin sensitivity, initially (P = .01) and with mutual adjustment (P = .05), was related to SHBG. Better insulin sensitivity initially (P = .12) was related to dihydrotestosterone and was attenuated by 60% with mutual adjustment (P = .69), according to the researchers. Overall, there were 112 incident cases of diabetes. Researchers observed no statistically significant relationship between free testosterone levels and the risk for diabetes. In initial models, the risk for diabetes was 21% lower with higher dihydrotestosterone levels (P = .009), the researchers wrote. “Because [dihydrotestosterone] is difficult to measure routinely, this isn’t quite ready for clinical use, but it may help to explain the confusing relationships between testosterone and diabetes found in earlier studies,” Mukamal told Endocrine Today. “Additional studies confirming these findings, particularly in younger men and women, who were not included in our study are needed.”