The Online Encyclopedia and Dictionary







A prohormone is a chemical compound that is a precursor to an actual hormone (usually an anabolic like testosterone or some variant), which is taken in order to boost the body’s available hormone supply. These precursors convert to full, active hormones via an enzymatic process that occurs during metabolism, typically resulting in the addition of whichever atoms happen to be missing from the chemical structure of the compound.

The use of prohormones has become popular among bodybuilders, since the effects can be similar (though normally much less drastic) to those achieved through the use of synthetic steroids, including gains in muscular strength and growth of lean muscle mass. There are currently many companies manufacturing prohormone products for this purpose.

Prohormones are legally sold in most parts of the world and are classified in the United States by the FDA as dietary supplements because they consist of compounds that occur naturally in the human body; however their use remains quite controversial and side effects are not uncommon. To date most prohormone products have not been thoroughly studied, and the health effects of prolonged use are mostly unknown.

On October 22nd, 2004, President Bush signed into law the Anabolic Steroid Control Act of 2004 (S.2195). The bill was written to become effective in 90 days, which as of this writing would appear to be January 20, 2005. This new legislation places both anabolic steroids and prohormones on a list of controlled substances.

Common types of prohormones on the market

  • 4-androstenedione
    • Converts to: testosterone
    • Characteristics:
      • Research indicates a conversion rate of about 5.6%, which means that of the amount taken orally, 5.6% is converted to testosterone.
      • Relatively high rate of aromatization to estrogen, and consequently higher risk of side-effects such as gynecomastia brought on by excessive estrogen formation.
      • Exhibits significant androgenic properties, which may result in side effects such as male pattern baldness, acne, and enlarged prostate.
  • 4-androstenediol (4-AD)
    • Converts to: testosterone
    • Characteristics:
      • Conversion rate of about 15.76%, almost triple that of androstenedione, due to utilization of a different enzymatic pathway.
      • No direct conversion to estrogen, though some secondary aromatization does occur through metabolism.
      • Appears to be less androgenic than its cousin, since it does not metabolize into the potent androgen dihydrotestosterone (DHT).
  • 19-norandrostenedione
    • Converts to: nortestosterone (also called nandrolone)
    • Characteristics:
      • Only slightly less anabolic than testosterone.
      • Low rate of aromatization to estrogen.
      • Low occurrence of androgenic side effects.
  • 19-norandrostenediol
    • Converts to: nortestosterone
    • Characteristics:
      • Same as -dione, except (as with the andros), the conversion rate is higher.
  • 1-androstenediol (1-AD)
    • Converts to: 1-testosterone a.k.a 1-Dihydrotestosterone, 1-DHT (a 5-alpha reduced form of testosterone reported to be 700% more anabolic and 200% more androgenic)
    • Characteristics:
      • Very high conversion rate, owing to the fact that the liver serves primarily to "activate" the compound as it passes through rather than to break it down and excrete it, as is the case with other prohormones.
      • Cannot aromatize to estrogen either directly or through any of its metabolic products. However,1-Testosterone is highly androgenic being a Dihydrotestosterone derivative. Many side effects associated with excessive levels of DHT, including male pattern baldness, testicular shrinkage, benign prostate hypertrophy and acne can occure with 1-AD usage. (Journal of Organic chem. vol, 27 1962 iss.1)
      • As with other -diols, .

External links

  • Prohormones, Athletes guide to prohormones for building muscle size and strength
Last updated: 05-07-2005 02:25:10
Last updated: 05-13-2005 07:56:04