Insulin suppresses testosterone?
Would you like the truth or more bullshit?
The truth is little is known, especially in men, about the direct relationship of insulin and testosterone.
[quote]Little is known about the interaction between testosterone levels and insulin sensitivity in men, in contrast to the abundant literature on this relationship in women (6). Cross-sectional studies demonstrate an inverse relationship between testosterone and fasting insulin levels in men independent of age, obesity, and body fat distribution (7?11). A link between testosterone deficiency and diabetes has also been suggested with the demonstration that men with type 2 diabetes have lower testosterone levels than weight-matched nondiabetic control subjects (12,13).
In addition, six large prospective studies have shown that low testosterone levels predict development of type 2 diabetes in men (14?19). Two studies demonstrate a positive relationship between total testosterone levels and insulin sensitivity in normal (20) and diabetic men (21). In contrast, data on the relationship between free testosterone levels and insulin sensitivity are conflicting, with two studies showing no correlation (21,22), whereas a third study demonstrates a weak positive relationship (20).[/quote]
[quote]There are no studies in vivo on the effects of insulin on androgens and sex hormone-binding globulin (SHBG) in men. We, therefore, investigated the effects of insulin suppression on testosterone and SHBG in two groups of eight nondiabetic adult obese men and six healthy normal weight men who underwent diazoxide treatment (100 mg, three times daily) for 7 days. Blood samples for hormone determination were obtained before the subjects had been selected for the study, immediately before diazoxide administration, and on the last day of treatment.
A 24-h oral glucose tolerance test was also performed for glucose, insulin, and C-peptide determinations before and on the last day of treatment. Only one subject experienced significant side-effects, and no significant changes in mean body weight were found during the treatment. Diazoxide administration worsened glucose tolerance in several subjects and reduced fasting and glucose-stimulated insulin levels by approximately 50% in both control and obese subjects. No significant difference was present between historical and pretreatment hormone values in either group.
Moreover, there were no differences in pretreatment gonadotropin and SHBG concentrations between the two groups, whereas testosterone (free and total) levels were lower in the obese than in the control subjects. After diazoxide administration, testosterone (free and total) decreased slightly, but significantly, whereas LH and SHBG significantly increased in both groups. Diazoxide treatment increased estradiol levels in controls, but not in obese men. In conclusion, these results indicate that in vivo, insulin is capable of stimulating testosterone production and, simultaneously, of inhibiting SHBG concentrations in both normal weight and obese men.[/quote]