Nandrolone

Nandrolone binds to the androgen receptor (AR) with affinity comparable to testosterone, promoting nitrogen retention, protein synthesis, and satellite cell activation in skeletal muscle tissue. Its anabolic effects are mediated through AR-dependent gene transcription that upregulates muscle-specific proteins including myosin heavy chain and IGF-1. A key distinguishing feature of nandrolone is its interaction with 5-alpha reductase: unlike testosterone, which is converted to the more potent androgen dihydrotestosterone (DHT), nandrolone is reduced to dihydronandrolone (DHN), a weaker androgen. This results in lower androgenic activity in tissues rich in 5-alpha reductase (skin, prostate, hair follicles). Nandrolone also stimulates collagen synthesis and bone mineral content through direct effects on osteoblasts and fibroblasts, contributing to its well-documented benefits for joint and connective tissue health. It exhibits moderate progestogenic activity, binding to the progesterone receptor at approximately 20% the affinity of progesterone, which can influence prolactin levels and contribute to progesterone-related side effects. Nandrolone aromatizes to estradiol at roughly 20% the rate of testosterone, resulting in lower but not absent estrogenic activity.