Once we have added in the necessary testosterone, the next step is controlling the impending estrogen and progesterone activity that will result from the use of the Nandrolone hormone. This makes the use of anti- estrogens highly recommended; most will need an Aromatase Inhibitor (AI). However, if we suppress estrogenic activity too much, this can lead to complications; it can lead to sexually related side effects as well as damage cholesterol. Conversely, if we do not control estrogen and let the hormone run wild, high levels of estrogen can lead to gynecomastia , water retention and also negatively affect sexual function. Find the right balance of testosterone to estrogen and you will not have a problem when stacking Deca Durabolin.
Sex hormone-binding globulin (SHBG) is thought to mainly function as a transporter and reservoir for the estradiol and testosterone sex hormones. However it has also been demonstrated that SHBG can bind to a cell surface receptor (SHBG-R). The SHBG-R has not been completely characterized. A subset of steroids are able to bind to the SHBG/SHBG-R complex resulting in an activation of adenylyl cyclase and synthesis of the cAMP second messenger.  Hence the SHBG/SHBG-R complex appears to act as a transmembrane steroid receptor that is capable of transmitting signals to the interior of cells.
How might behaviors affect hormones? The birdsong example demonstrates how hormones can affect behavior, but as noted, the reciprocal relation also occurs; that is, behavior can affect hormone concentrations. For example, the sight of a territorial intruder may elevate blood testosterone concentrations in resident male birds and thereby stimulate singing or fighting behavior. Similarly, male mice or rhesus monkeys that lose a fight decrease circulating testosterone concentrations for several days or even weeks afterward. Comparable results have also been reported in humans. Testosterone concentrations are affected not only in humans involved in physical combat, but also in those involved in simulated battles. For example, testosterone concentrations were elevated in winners and reduced in losers of regional chess tournaments.