Due to its chemical structure nandrolone is weakly exposed to aromatase (only 20% of the aromatizing activity of testosterone). However, not estrogenic effects are its main concern: nandrolone has a potent progestogenic activity (20% of progesterone). While binding to progestogenic pituitary receptors nandrolone causes increased production of prolactin, which in effect is very similar to estradiol. To prevent these side effects prolactin inhibitors (cabergoline) shall always be at hand when on nandrolone cycle.
Nandrolone has become a name in sports and bodybuilding due to its ability to promote quantity and quality in bodybuilding. It promotes protein synthesis in the body, which is essential in building body mass and additional strength. As a relatively mild steroid (androgenic activity index: 37% as compared to testosterone), it can be used even by women and those concerned with hair loss because androgenic / virilization effects are less likely to develop.