Testosterone hydroalcoholic gel is applied daily (preferably in the morning) to intact, clean, dry skin of the shoulders, upper arms, and/or abdomen. Patients should be careful about transferring testosterone to their female partner(s). The prescribing information for AndroGel® suggests that patients wash their hands immediately with soap and water after application, and also recommends covering the application site(s) with clothing after the gel has dried. Studies with AndroGel® have demonstrated that female partners of male patients noticed as much as a doubling of serum testosterone levels following 15 minutes of rigorous skin-on-skin contact. This contact was initiated between 2 and 12 hours after drug administration. Testosterone transfer was completely avoided when the male subjects wore a shirt.
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.