Insulin regulates testosterone and sex hormone-binding globulin concentrations in adult normal weight and obese men.

Abstract

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.

Acute decrease in serum testosterone after a mixed glucose and protein beverage in obese peripubertal boys

“…14,24 The 60-min time point was chosen as a previous study in adults has indicated postglucose load nadir testosterone values at this time. 11 In a separate visit conducted within 4 weeks of the visit described above, body composition was analysed via BOD POD (Life Measurement Incorporated, Concord, CA, USA) air-displacement plethysmography (ADP). 25 A standard, calibrated scale and wall-mounted stadiometer were used to measure weight and height, and body mass index (BMI) was calculated as weight (kg)/height (m) 2 .…”

Androgens, insulin resistance and vascular disease in men

“…Furthermore, Pasquali et al . 38 demonstrated that inhibition of insulin secretion by giving diazoxide to normal weight and obese men led to increased SHBG levels. Acute hyperinsulinaemia has also been found to result in a small but significant reduction in SHBG concentration in healthy men.…”

Effects of intraperitoneal insulin versus subcutaneous insulin administration on sex hormone-binding globulin concentrations in patients with type 1 diabetes mellitus

“…Although the exact mechanism remains unknown, an inhibitory effect of insulin on the synthesis of SHBG seems a valid explanation, as direct inhibition of SHBG synthesis by insulin has been observed in HepG2 cells in the liver, both in vitro and in vivo (1, 6, 9, 14, 15, 16). Since there is (almost) no endogenous insulin production in T1DM patients, an increase of portal insulin concentration with CIPII and the subsequent increased hepatic insulinization may cause a more pronounced suppression of SHBG production.…”

“…Since there is (almost) no endogenous insulin production in T1DM patients, an increase of portal insulin concentration with CIPII and the subsequent increased hepatic insulinization may cause a more pronounced suppression of SHBG production. Apart from portal insulin concentrations, other factors such as glycemic control, insulin dose, insulin resistance, and the presence of microvascular complications have been suggested to influence SHBG concentrations (1, 4, 14, 17) among T1DM patiets.…”

“…Previous research has demonstrated that SHBG concentrations are inversely associated with (fasting) insulin concentrations in vivo (1, 6, 9, 14, 15, 16). Furthermore, in vitro , insulin has an inhibitory effect on the basal and stimulated SHBG production by HepG2 cells of the liver (17).…”