Experimenting on using male hormone DHT transdermally on the penis to signal growth, let me explain how I understand the whole thing. First there is testosterone, which circulates in the blood and attaches and detaches from the androgen receptor sites in the body. Next, to control the level of testosterone, the body needs a way to destroy it. One of the possible ways is to use an alpha-reductase enzyme , which cleaves testosterone and the pieces it leaves behind is called d ihydrotestosterone (dht) . Dht is highly androgenic, which means that it attaches to the androgenic receptor sites longer and stronger. The penis contains a concentration of androgenic receptors, and if these receptors are saturated with dht hormone continuously, new cells (each containing more androgen receptors) are grown to help accommodate the local load of dht. (This is only speculation, as I am not an expert in this field.) However, if dht is taken over long periods of time, the body will shut down testosteron