The side effects of Nebido can include those of an androgenic nature. The androgenic side effects of Nebido are, however, highly dependent on genetic predispositions and will not affect all men. The possible androgenic side effects of Nebido include accelerated hair loss in those predisposed to male pattern baldness, acne in sensitive individuals and body hair growth.
While by no means always necessary, some men may find the use of a 5-alpha reductase inhibitor to be useful. The testosterone hormone is metabolized by the 5-alpha reductase enzyme, which reduces the testosterone hormone to dihydrotestosterone (DHT). The DHT is what leads to the androgenic related effects. By incorporating a 5-alpha reductase inhibitor, you will reduce the hormones androgenicity. It will not be a complete reduction, but it will be significant. However, such inhibitors are not always recommended and should only be used as needed as they can hinder the potency of the testosterone hormone.
Because steroids are lipophilic, they diffuse easily through the cell membranes, and therefore have a very large distribution volume. In their target tissues, steroids are concentrated by an uptake mechanism which relies on their binding to intracellular proteins (or " receptors ", see below). High concentration of steroids are also found in adipose tissue, although this is not a target for hormone action. In the human male, adipose tissue contains aromatase activity, and seems to be the main source of androgen-derived estrogens found in the circulation. But most of the peripheral metabolism occurs in the liver and to some extent in the kidneys, which are the major sites of hormone inactivation and elimination, or catabolism (see below).
Because non-genomic pathways include any mechanism that is not a genomic effect, there are various non-genomic pathways. However, all of these pathways are mediated by some type of steroid hormone receptor found at the plasma membrane.  Ion channels, transporters, G-protein coupled receptors (GPCR), and membrane fluidity have all been shown to be affected by steroid hormones.  Of these, GPCR linked proteins are the most more information on these proteins and pathways, visit the steroid hormone receptor page.