I can confirm this to be true. I get my testosterone checked regularly along with my TSH numbers. For some reason my TSH is never a consistent number and my testosterone levels have been in the crapper for a long time. Even with testosterone supplements my levels didn’t improve much, if at all. Last July my doctor said my PSA numbers were a bit high so he told me to stop taking the Andriol, the testosterone supplement. Fast forward to December when I started taking 2000 IU of vitamin D per day. I had my blood tested again a few weeks ago at the end of February and my doctor said my testosterone levels were higher than they’ve been over the last few years while taking supplements.
The use of anabolic-androgenic steroids (AS) by athletes to enhance their athletic performance has been reported since the 1950s Androgen use has spread to different groups of athletes, who use these drugs for various reasons. The common thread among all these groups, however,is the goal of enhancing muscular capacities and athletic performance and being successful (winning). Androgen use by weightlifters in order to enhance strength and thereby perform better in an event in which there is a direct correlation between strength and success is well known.
DHT is a potent agonist of the AR, and is in fact the most potent known endogenous ligand of the receptor. It has an affinity (K d ) of to nM for the human AR, which is about 2- to 3-fold higher than that of testosterone (K d = to nM)  and 15–30 times higher than that of adrenal androgens .  In addition, the dissociation rate of DHT from the AR is 5-fold slower than that of testosterone.  The EC 50 of DHT for activation of the AR is nM, which is about 5-fold stronger than that of testosterone (EC 50 = nM).  In bioassays , DHT has been found to be - to 10-fold more potent than testosterone.