Nandrolone (also sold under the trade names Retabolil and Deca Durabolin, chemical name 19-nortestosterone) is an anabolic steroid that is naturally present in the blood of everyone in small amounts.

Nandrolone is most commonly sold in the decanoate form, less often in the phenylpropionate form. Deca Durabolin first appeared on the market in 1962 and has been one of the most popular steroids in recent decades, earning its reputation for strong anabolic activity and relatively low incidence of side effects.

Retabolil is still sold in pharmacies (from the company Gedeon Richter JSC VEN, 50 mg / ml, ampoules). Released according to the prescription form N 148-1 / y-88.

Structurally, nandrolone differs from testosterone in the absence of a carbon atom at position 19 (hence the name 19-nortestosterone) and this makes it more similar to progestins.

Due to its progestin nature, retabolil exhibits significantly less androgenic effect compared to testosterone, however, interaction with progesterone receptors entails a number of side effects, which will be described below.

Another difference is that testosterone in the body is gradually converted by the enzyme 5-alpha reductase into a powerful androgen, dihydrotestosterone, which is responsible for most of the side effects.

Nandrolone, on the contrary, is converted by 5-alpha reductase into an extremely weak androgen - dihydronandrolone, which has practically no effect on the body and does not cause side effects.

However, this may be one of the reasons for a decrease in libido during the course (due to a drop in blood androgen levels). It should be added that dihydronandrolone is sometimes included in some anabolic supplements, although it does not present much benefit.