Data from two observational registries indicated that long-term testosterone replacement therapy in diabetic men was associated not only with better sexual function and weight loss, but also significant reductions in blood sugar.
Indeed, A1c levels typically fell by two percentage points over the course of seven or eight years of treatment — a huge effect considering that metformin and other diabetes medications typically reduce A1c by roughly one percentage point.
Both studies, which were presented at the American Urological Association Annual Meeting in New Orleans, also noted significant declines in fasting blood sugar levels.
The first of those studies followed 77 hypogonadal diabetics from Hamburg, Germany for up to 11 years. All of the men received testosterone injections, which increased their total testosterone levels from an average of 7.6 nmol/L at the beginning of the study to 17-20 nmol/L at the 8-year follow-up. Free testosterone levels rose from150 pmol/L to 400-500 pmol/L over the same period.
Average scores on the erectile function section of the International Index of Erectile Function rose from 6.14 at baseline to 18.22 at eight years. Patient weight, on the other hand, declined an average of 18.24% (p<0.0001), while average waist circumference fell from 115.03 cm to 96.47 cm (p<0.0001).
As for blood sugar, the average patient’s fasting glucose level fell from 146.26 mg/dL to 83.72 mg/dL (p<0.001) over 8 years of treatment and the average patient’s A1c level fell from 7.87% to 5.99%.
The second of the studies followed 120 hypogonadal diabetics for up to seven years. All the men received testosterone injections, which boosted average testosterone levels from 10 nmol/L at baseline to 15-18 nmol/L at 7 years.
The cohort in this study started off, on average, with better scores on the erectile function index, but those scores still rose, from 19.7 to 25.2 over the course of seven years. The average weight loss was the same as in the first study — 18.24% of initial body mass — and there was significant improvements to patient lipid profiles and blood pressure readings. Average body mass index fell from 35.57 to 29.09 (p<0.0001), while average waist circumference fell from 109.3cm to 99.9cm (p<0.0001).
The reduction in the average fasting glucose level was not quite so great as in the first study; it dropped from 113.45 mg/dL to 95.93 mg/dL. The reduction in the average A1c level, on the other hand, was nearly identical; it dropped from 8.02% to 5.9%.
Lead study author Abdulmaged Traish, PhD, of the Boston University School of Medicine noted that only 11% of the diabetic patients met recommendations to keep A1c levels under 7% when the study began but that all of them did so by the time it ended.
Testosterone’s long-demonstrated ability to reduce patient body weight, along with the long-demonstrated tie between obesity and diabetes, has suggested to many that the hormone could be helpful to the majority of diabetic men who are also hypogonadal, but different studies have reached different conclusions.
Just last year, a 6-month study conducted by University of Buffalo researchers on 41 hypogonadal diabetics found that testosterone had significant impact on insulin resistance, glucose infusion and other key metabolic metrics. A 6-month study conducted by Australian researchers on 88 similar men, however, found just the opposite.
The authors of the new studies believed that the length of treatment, combined with the size of the measured associations, provide strong evidence that testosterone replacement could significantly reduce the harm that hypognadic men suffer from diabetes.