inuslin lower SHBG levles.
Lower levles of SHBG= More free testostrone.
TRUE
Journal of Clinical Endocrinology & Metabolism, Vol 80, 654-658, Copyright © 1995 by Endocrine Society
Insulin regulates testosterone and sex hormone-binding globulin concentrations in adult normal weight and obese men
R Pasquali, F Casimirri, R De Iasio, P Mesini, S Boschi, R Chierici, R Flamia, M Biscotti and V Vicennati
Institute of Clinical Medicine 1, Endocrine Unit, Bologna, Italy.
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.
Sex Hormone–Binding Globulin and Testosterone in Individuals With Childhood Diabetes
Kirstie K. Danielson, PHD1, Melinda L. Drum, PHD2 and Rebecca B. Lipton, PHD, MPH, BSN1,2
1 Institute for Endocrine Discovery and Clinical Care, University of Chicago, Chicago, Illinois
2 Department of Health Studies, University of Chicago, Chicago, Illinois
Corresponding author: Kirstie K. Danielson, PhD, 5841 S. Maryland Ave., MC5053, Chicago, IL 60637. E-mail:
[email protected]
OBJECTIVE—Insulin downregulates hepatic production of sex hormone–binding globulin (SHBG), which in turn influences sex hormone bioavailability. The effects of childhood-onset diabetes and insulin resistance in nondiabetic individuals on SHBG and testosterone in children and young adults are poorly understood.
RESEARCH DESIGN AND METHODS—Individuals with diabetes diagnosed at <18 years of age (n = 48) and their siblings without diabetes (n = 47) were recruited for the Chicago Childhood Diabetes Registry Family Study. SHBG and total and free testosterone were measured. Participants ranged in age from 10 to 32 years; 39% were non-Hispanic white. The majority of individuals with diabetes had the classic type 1 phenotype (75%), while the remainder exhibited features of type 2 or mixed diabetes; 96% were treated with insulin.
RESULTS—SHBG and total testosterone were higher in male subjects with diabetes compared with those in male siblings. Elevated SHBG was associated with the absence of endogenous insulin independent of sex; elevated total testosterone was similarly associated with the absence of C-peptide for male subjects only. Diabetes type and treatment were unrelated. In those without diabetes, greater insulin resistance had a small, nonsignificant association with lower SHBG and higher free testosterone.
CONCLUSIONS—SHBG and total testosterone appear to be higher in male children and young adults with diabetes compared with nondiabetic male siblings, which is apparently related to the absence of endogenous insulin. This may have implications for sex hormone–dependent processes across the lifespan in male individuals diagnosed with diabetes as children.
Abbreviations: HOMA, homeostasis model assessment • SHBG, sex hormone–binding globulin