As shown in table 5, testosterone therapy markedly reduced the number of medications needed to control diabetes. In the low testosterone/untreated group 14.3%, 28.6%, 38.1%, and 17.1% of men were on 0, 1, 2, and ≥3 medications, respectively. The corresponding figures for the low testosterone/treated/stopped and low testosterone/treated/continuous groups were 12.8%, 41.0%, 25.6%, 20.5% and 48.8%, 41.5%, 4.9%, 4.9%, respectively.
Table 5: Number of medications prescribed to control diabetes in untreated and testosterone treated men.
|Number of diabetes medications used among men (%)
|0 medication (diet only)
This is the first longitudinal long-term study (mean follow-up, 3.8 years) to describe the effect of testosterone therapy in men with type 2 diabetes undergoing routine primary care diabetes treatment of glycemic control.18
Reduction in waist circumference with concomitant body weight gain
In the group of men who continued testosterone therapy throughout the entire 4-year follow-up, a particularly interesting finding was observed; body weight and waist circumference both decreased significantly until the end of the 82-week period, thereafter body weight started to increase while waist circumference continued to decrease.18 In contrast, in the group of men who discontinued testosterone therapy after the 82-week time point, both body weight and waist circumference increased in tandem. This suggests that men who continued testosterone therapy long-term had an increase in lean mass (presumably muscle mass). Support for this interpretation comes from a randomized controlled trial showing that testosterone therapy can increase lean body mass by 3 kg while simultaneously reduce fat mass by the same amount, resulting in no change in body weight but a dramatic improvement in body composition and metabolic control.19 Thus, sole reliance on body weight and BMI can be very misleading by disguising valuable improvement in body composition, which in turn is associated with increased muscle strength, physical fitness and reduced frailty.20 This underscores the importance of measuring changes in waist circumference along with changes in body weight in clinical practice.
Continuous long-term improvement in erectile function
Another notable finding in this study is that in men who discontinued testosterone therapy after 82 weeks, improvements in HbA1c and erectile function that were achieved during testosterone therapy quickly started to deteriorate. In contrast, among men who continued testosterone therapy for 4 years, erectile function continued to markedly improve. This progressive marked improvement in erectile function for nearly 4 years - independent of PDE5I – is highly remarkable as it was previously believed that maximal improvements in erectile function are usually achieved after 3-6 months of testosterone therapy.21 Several clinical guidelines recommend that men with borderline hypogonadism should be given a therapeutic trial of testosterone therapy for 3 months22, 6 months23 or 12 months24 to see if it works. Erectile dysfunction is one of the primary symptoms associated with hypogonadism25 and therefore improvement in erectile function is a major measure of the effectiveness of testosterone therapy. Hence, it is critical for healthcare professionals to be informed that patients with hypogonadism who have been on testosterone therapy for 3-12 months but not experienced the expected improvement in erectile function yet will likely do so if they stay on testosterone therapy consistently for a longer time period.
It has been stated that PDE5I and not testosterone therapy should be the first-line treatment for men with erectile dysfunction.26 However, data support the practice of combining PDE5I with testosterone therapy because each has independent beneficial effects on erectile function, as well as reduced all-cause mortality.16,17
Reduced requirement of diabetes medications in men receiving testosterone undecanoate treatment
An additional important finding in this long-term study is that men on continued non-interrupted long-term testosterone undecanoate treatment required fewer medications to control their diabetes. This is of major clinical importance and could potentially have a significant impact on healthcare practice. Testosterone is known as being the “libido hormone”, but it is a powerful metabolic hormone as well.27 The reduced requirement for diabetes medications in this study is in accordance with data from more longer-term studies, which have demonstrated that testosterone therapy for at least 7 years can result in remission of type 2 diabetes and complete discontinuation of diabetes medications.3,8