New research presented at this year's annual meeting of the European Association for the Study of Diabetes (EASD) reveals that in men with low testosterone who have type 2 diabetes (T2D), testosterone therapy can improve their disease and reverse its progress, and can also induce significant weight loss.
The research was conducted by Dr Farid Saad, Bayer AG, Berlin, Germany, and colleagues. The aim of the study was to determine the effect of long-term testosterone therapy (TTh) on hypogonadal men (those with low testosterone production) who had T2D. Numerous experimental and clinical studies have shown that TTh can have beneficial effects in hypogonadal men with T2D.
The study population was selected from a group of 805 men with low testosterone, of whom 311 had T2DM and participated in the research. These were split into two groups; a T-group of 141 men who opted for TTh and were given 1000mg injections of testosterone undecanoate every 12 weeks, and the remaining group of 170 men who did not wish to receive this treatment acted as the control group.
The participants were followed up 1-4 times per year when blood samples were taken and their weight and waist measurements were recorded. Their diabetic state was quantified by measuring fasting blood glucose and glycated haemoglobin (HbA1c); levels of which both rise in diabetic patients due to the body having poor control over blood sugar. Fasting glucose gives a measurement of the current state of blood sugar, while HbA1c acts as a measure of the 3-month average of blood glucose levels.
By the end of the 10-year follow-up period, average fasting blood glucose levels decreased in the T-group from 7.7 to 5.3 mmol/L, while in the control group, it rose from 6.3 to 8.2 mmol/L. Average levels of HbA1c also fell in the T-group from 9.0 to 5.9%, and increased in the control patients from 7.8 to 10.6%. This indicated that among the T-group, their T2DM had become less severe, while it had worsened in the untreated controls.
The 61 patients in the T-group who relied on insulin to control their diabetes were able to reduce their dose significantly, falling from an average 34 to 19.9 units per day. Members of the untreated control group saw their average insulin dose rise from 30.7 to 42.2 units per day.
Changes were also observed in weight and waist size measurements of participants. Average weight of T-group members reduced from 113.4 to 90.7 kg at the end of the 10-year study period, and their average waist size dropped from 112.6 to 99.6 cm. Weight and waist circumference of untreated control group patients remained stable throughout the period of the research and no significant reduction of either was observed.
Patients with diabetes are often given a target HbA1c level as a way of measuring the success of any treatments for their disease, which is typically set at either 6.5 or 7.0%. In the control group, there were no patients who reached either target, while in the T-group 80.1% achieved the 6.5% target, and 90.8% reached the 7.0% HbA1c level by the time of the last measurement. Those who did not reach their targets were men who had been treated with testosterone for the shortest duration.
One of the concerns with testosterone therapy in middle aged and elderly men is the persistent fear of inducing prostate cancer. The authors say guidelines by both the European and American Associations of Urology agree that there is no evidence for this assumption. In the present study, the incidence of prostate cancer was in fact twice as high in the untreated control patients as in the testosterone-treated patients.
"The other concern is an increase in haemoglobin and haematocrit which, however, may be a beneficial effect of testosterone rather than a side effect. Testosterone effectively treats anaemia which is not so rare in an elderly population, and anaemia itself presents a cardiovascular risk," explains Dr Saad. "A substantially elevated haematocrit occurred very rarely in this study and was always transient in that it returned to normal with the next measurement. There was not a single heart attack or stroke in the testosterone-treated group, events one may associate with an increase in haematocrit."
The authors conclude: "Long-term testosterone therapy can support diabetes treatment in hypogonadal men with T2D. Its use improved the control of blood glucose, while it deteriorated in patients who had opted not to receive TTh. There were also significant reductions in both weight and waist size in the T-group, which we suggest could have contributed to the observed effects."
Patients in the T-group who were on insulin could have their dose substantially reduced, and the team note that: "Since all injections were administered in the doctor's office and documented, we know that there was 100% adherence to the testosterone therapy used in this study."
They plan a continuation of this registry study for at least another 5 years. They add: "The results, especially in the diabetic subgroup, are becoming increasingly interesting as we had the first patients who went into remission, some after as many of 10 years of testosterone treatment."