4-Andro or 4-Androstenediol, also known as androst-4-ene-3β,17β-diol, is an androstenediol that is converted to testosterone. The conversion rate is about 15.76%, almost triple that of 4-androstenedione, due to utilization of a different enzymatic pathway. There is also some conversion into estrogen, since testosterone is the metabolic precursor of the estrogens.
4-Androstenediol is closer to testosterone structurally than 5-androstenediol, and has androgenic effects, acting as a weak partial agonist of the androgen receptor. However, due to its lower intrinsic activity in comparison, in the presence of full agonists like testosterone or dihydrotestosterone (DHT), 4-androstenediol has antagonistic actions, behaving more like an antiandrogen. So, it would not be a beneficial Performance Enhancer to stack with injectable Anabolic Androgenic Steroids (AAS).
4-Androstenediol is very weakly estrogenic. It has approximately 0.5% and 0.6% of the affinity of estradiol at the ERα and ERβ, respectively.
Chen, et al. (2004) demonstrated “A-diol bound full-length endogenous [Androgen Receptor] AR from MDA or LNCaP cells with affinities of 30-70nM, although binding to expressed ligand-binding domain (LBD) was >20-fold weaker. In contrast, DHT, R1881, and bicalutamide bound similarly to LBD or aporeceptor. Together, these data suggest that A-dione and A-diol are ligands for AR with partial agonist/antagonist activities in cell-based transcription assays. Binding affinities for both are most accurately assessed by AR aporeceptor complex. In addition to being testosterone precursors in vivo, either may impart its own transcriptional regulation of AR.”
And from Patrick Arnold’s original 1999 patent on this compound:
“In the course of our research, we have found that the blood testosterone level increases seen with the oral administration of androstenedione are far less and more variable than what is described in U.S. Pat. No. 5,578,588. It was therefore an object of this invention to discover another naturally occurring testosterone precursor that provided a greater blood testosterone level response than androstenedione but retained all the advantages of being a non-toxic, natural, and quickly metabolizable precursor. This would therefore permit oral administration at a reasonable dose providing a dependable therapeutic response.
The chemical term 4-androstenediol refers to two isomers: 4-androstene-3beta, 17betadiol and 4-androstene-3alpha, 17beta-diol. This invention concerns primarily the former isomer in the preferred embodiment.
4-androstenediol is a naturally occurring compound. It has been identified as a metabolite of testosterone in placental, uterine, testicular, adrenal, and hypothalamic/pituitary tissues. It acts as a very effective precursor to testosterone. 4-androstenediol converts to testosterone via the 3beta-hydroxysteroid dehydrogenase enzyme. F. Ungar, M. Gut, and R. Dorfman (J Biol. Chem., 224, 191-200) found that after 4-androstenediol was incubated in liver tissue it metabolized very readily to testosterone. J. Blaquier, E. Forchielli, and R. Dorftnan (Acta Endocrinologica, 55, 697-704) also revealed that the in vitro conversion of tritiated 4-androstene-3beta, 17betadiol to testosterone in whole human blood was very efficient (15.76%) and was in fact considerably more efficient that tritiated androstenedione (5.61%).
After learning of the in-vitro efficacy of 4-androstenediol in regards to testosterone conversion, it was then the intention of the inventor to investigate whether 4-androstenediol would act as an effective in-vivo peroral testosterone precursor in humans. It was also the intention of the inventor to investigate whether or not 4-androstenediol would act as a superior peroral testosterone precursor to androstenedione.”
Essentially, this compound can effectively raise testosterone and its downstream effects of activation of the androgen receptor including increased myonuclear genesis leading to long term, and maybe permanent, increased potential for muscular growth and strength.