A Randomized Double-Blind Placebo-Controlled Pilot Trial on the Effects of Testosterone Undecanoate Plus Dutasteride...

While the effects of androgens on muscle are well described in hypogonadal men, literature is still scarce on muscular strength or size variations in transmen; in this population there are no data regarding the relative effect of testosterone (T) and its metabolite dihydrotestosterone on muscle.

Our primary objective was to compare the effects on muscle strength of 54-week administration of testosterone undecanoate (TU) combined with the 5α-reductase inhibitor dutasteride (DT) or placebo (PL). Secondary outcomes included evaluation of body composition, bone, cutaneous androgenic effects, and metabolic variations.

In this randomized, double-blind PL-controlled pilot trial, 16 ovariectomized transmen were randomized to receive TU 1,000 mg IM at week 0, 6, 18, 30, 42 plus a PL pill orally daily (TU + PL, n = 7) or plus DT 5 mg/d (TU + DT, n = 7).

At week 0 and 54 the following parameters were evaluated: isokinetic knee extension and flexion peak torque and handgrip strength, body composition, and bone mineral density, biochemical, hematological, and hormonal parameters.

Handgrip and lower limb strength increased significantly in both groups with no differences between the 2 groups. Fat mass decreased and lean mass increased significantly similarly in both groups. Metabolic parameters remained stable in the 2 groups except for high-density lipoprotein cholesterol that was reduced in both groups. Hepatic and renal function remained normal in both groups and no major adverse effects were registered in either group.

These results may be particularly relevant for transmen experiencing cutaneous androgenic adverse events such as acne and androgenetic alopecia and in light of the development of non-5α-reduced androgens.

The strength of this study was the randomized, double-blind PL-controlled design, while the small number of subjects was definitely the biggest limitation.

For the first time we demonstrated that the addition of DT does not impair the anabolic effects of T on muscles in transmen previously exposed to T, supporting the hypothesis that the conversion in dihydrotestosterone is not essential for this role. Gava G, Armillotta F, Pillastrini P, et al. A Randomized Double-Blind Placebo-Controlled Pilot Trial on the Effects of Testosterone Undecanoate Plus Dutasteride or Placebo on Muscle Strength, Body Composition, and Metabolic Profile in Transmen. J Sex Med 2021;18:646-655.