I went back and looked at a couple of old papers on nandrolone (Belkien et al., 1984 and Schurmeyer et al., 1984).
In the Belkien study a single 50 mg dose of Deca (ND) suppressed T for up to 20 days. The threshold level of nandrolone in blood to have an effect on T was about 1 nmol/l, which was still present on day 15 after the single 50 mg dose. Blood levels of N peaked 1 day after the single injection at about 4.5 nmol/l and slowly fell to below 1 nmol/l at day 25.
In the Schurmeyer study they administered nandrolone hexoxyphenylpropionate (NP) (mean half-life about 21 d) for 13 weeks. 100 mg/wk first 3 weeks, then 200 mg/wk the next 10 weeks.
Following the last dose, it took 16 weeks for testicular volume to return to baseline, 16 weeks for LH and FSH to get back to baseline, and 24 weeks for T to return to baseline. There was no change in prolactin in this study during N administration. Nandrolone peaked at 20 nmol/l at 13 weeks in the blood, was still at 5 nmol/l and 1 nmol/l, 8 and 16 weeks out, respectively.
The measured half-life of both ND and NP were variable among subjects, 5 - 17d for ND and 4 - 34d for NP. It appears that there is considerable variation in clearance from subject to subject.
W6