Tissue Selectivity of the Anabolic Steroid, 19-Nor-4-Androstenediol-3β,17β-Diol in Male Sprague Dawley Rats: Selective Stimulation of Muscle Mass and Bone Mineral Density Relative to Prostate Mass

Abstract

Stimulation of prostate growth is a major concern with testosterone therapy in older hypogonadal men. As a result, nonsteroidal selective androgen receptor modulators with anabolic activity but less prostate stimulation are being developed. Anabolic steroids might exhibit similar tissue selectivity. We hypothesized the anabolic steroid 19-nor-4-androstenediol-3β,17β-diol (3β,19-NA) would increase muscle, lean body mass (LBM), and bone mineral density (BMD) with little stimulation of prostate growth. Male Sprague Dawley rats were implanted with SILASTIC brand (Dow Corning, Midland, MI) capsules containing 3β,19-NA (4, 8, or 16 cm), dihydrotestosterone (DHT) (8 cm), 19-nortestosterone (16 cm), or four empty capsules after undergoing either a sham operation (intact) or orchidectomy (ORX). Serum gonadotropins, measured after 4, 8, or 24 wk of treatment, were significantly lower in 3β,19-NA-treated vs. untreated, intact, and ORX rats (P < 0.05), and testosterone was lowered by 3β,19-NA-treatment of intact animals. LBM and BMD were assessed after 20 wk, and 4 wk later, rats were killed for levator ani muscle and prostate weights. Compared with ORX rats, 3β,19-NA-treated rats had dose-dependent higher levator ani muscle weights, LBM, and BMD, which were similar to intact and DHT-treated rats at the highest 3β,19-NA dose. In contrast, prostate weights in all 3β,19-NA-treated groups were similar to ORX rats and lower than intact and DHT- and 19-nortestosterone-treated rats even at the highest 3β,19-NA dose. In summary, 3β,19-NA increases muscle and bone mass without significant stimulation of prostate growth, suggesting it may have some properties of a steroidal selective androgen receptor modulator. Anabolic steroids such as 3β,19-NA should be studied further to determine their mechanisms of tissue selectivity and effects in men.