people often make the mistake of equating high androgen receptor (AR) binding affinity with androgenicity, probably because DHT possesses both properties. There is a notion, likely started by this paper (1) that the 5 alpha reduced version of nandrolone is a weaker androgen than the parent compound. The opposite is true with testosterone. Hence the often read admonition not to combine finasteride with Deca, because it would be bad for the hair and prostate. To quote from (1),
"In the accessory sex organs (e.g. the prostate) testosterone is 5 alpha-reduced to dihydrotestosterone (DHT) which, due to its higher affinity for androgen receptors (AR), amplifies the action of testosterone. In contrast, when 19-nortestosterone (NT) is 5 alpha-reduced, its affinity for AR decreases, resulting in a decrease in its androgenic potency."
In other In vivo studies the picture is different (2). Quoting from this paper,
"The results of AR binding studies revealed that 5alpha-reduction of T and ET significantly enhanced their affinities, and that the 5alpha-derivative of 19norT displayed a similar binding affinity to that exhibited by 19norT. In terms of biological activity, the results showed that 5alpha-reduction of T and 19norT significantly increased their androgenic potency..."
Here androgenic potency was determined in part by action on the prostate. So these two papers are completely at odds with one another, and I wouldn't assume that the commonly held belief that 5 alpha reduced nandrolone is a weaker androgen than the parent compound is necessarily true.
If you are worried about your prostate, avoid agents that are subject to 5 alpha reduction, and that have a low anabolic/androgenic ratio.
(1) J Steroid Biochem Mol Biol. 1995 Jun;53(1-6):253-7.
Different patterns of metabolism determine the relative anabolic activity of 19-norandrogens.
Sundaram K, Kumar N, Monder C, Bardin CW.
(2) J Steroid Biochem Mol Biol. 1997 Jan;60(1-2):121-9.
5alpha-reduction of norethisterone enhances its binding affinity for androgen receptors but diminishes its androgenic potency.
Lemus AE, Enriquez J, Garcia GA, Grillasca I, Perez-Palacios G