Rapid Changes in Serum Testosterone in Men with Newly Diagnosed Type 2 Diabetes With Intensive Insulin and Metformin
Methods: Seventy men with newly diagnosed drug naïve T2DM, HbA1c >9.0% (75mmol/mol) were treated with intensive insulin pump therapy for 5 days to achieve glucose normalization. They were randomized to control (continued on intensive insulin only) and metformin (plus metformin) groups (1:1) for one month. Testosterone was measured at baseline, randomization, and after one-month treatment.
Results: Total, free and bioavailable testosterone increased significantly within 5 days (all p<0.001). After one month, compared to controls, the metformin group had lower total (12.7 vs 15.3 nmol/L), free (0.20 vs 0.24 nmol/L), and bioavailable (4.56 vs 5.31 nmol/L) testosterone (p all <0.05).
Conclusions: In men with T2DM, one-month oral metformin may decrease serum testosterone levels independent of blood glucose control. The effects of long-term metformin on testosterone in men need further study.