Serum testosterone in Nigerian men with type 2 diabetes mellitus and its relationship with insulin sensitivity and glycemic control

Abstract

Background: There is increasing evidence that testosterone deficiency has key associations with insulin sensitivity and glycemic control. Its presence may therefore contribute to and/or exacerbate clinical disease in men with type 2 diabetes mellitus (T2DM). This study sought to determine the frequency of low free testosterone and explore its relationship with, insulin sensitivity and glycemic control among Nigerian men with T2DM.

Methods: One hundred and four men with type 2 DM and one hundred and one apparently healthy non-diabetic men matched for age, were recruited into the study Socio-demographic data, anthropometric measurements and blood samples were obtained for measurement of serum total testosterone (TT), sex hormone binding globulin (SHBG), fasting plasma insulin, fasting plasma glucose (FPG), glycated hemoglobin (HbA1c) and fasting lipid profile in all the subjects. Insulin sensitivity (%IS) and free testosterone (CFT) were then calculated.

Results: The median CFT for men with T2DM was significantly lower than that of non-diabetic controls (0.17 nmol/L vs 0.58 nmol/L respectively; P < 0.001). 52.9% of men with T2DM had low CFT, as compared with 21.4% amongst the non-diabetic controls; P < 0.001. Among men with T2DM, those with lower CFT had significantly lower median % S and higher mean HbA1c than those with normal CFT (37.0% versus 63.0%; P = 0.021 and 7.79 (2.03) % versus 7.02 (1.94) %; P = 0.038 respectively]. HbA1c had significant negative correlations with both CFT (correlation coefficient: -0.239 (P < 0.05) and TT (correlation coefficient: 0.354; P < 0.01. There was no significant difference in serum lipids when T2DM men with low serum CFT were compared with T2DM men with normal serum CFT levels.

Conclusion: We conclude that low serum testosterone is common among men with T2DM and has a significant association with glycemic control (HbA1c) and insulin sensitivity.

Keywords: Diabetes mellitus; Glycemic control; Insulin sensitivity; Testosterone.