Around fifth part of the injected steroid binds to progestin receptors (due to the absence of a carbon atom in the 19 position), and therefore, such reactions as the suppression of secretion of gonadotropin-releasing hormone, increased production of prolactin, a significant decrease in libido should not be excluded. Weak erection - the most pronounced and severe consequence of abuse of deca nandrolone. Exceeding of the recommended dosage and duration of the course may cause rhinitis, headache, back pain, rash. In general, the side effects of nortestosterone decanoate - rather the exception than the rule.
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 estrogen: its effect presents in reducing testosterone production, increasing fat mass and in gynecomastia. To prevent these side effects prolactin inhibitors (cabergoline) shall always be at hand when on nandrolones cycle.