Prohormone

A prohormone is a substance that is a precursor to a hormone, usually having minimal hormonal effect by itself. The term has been used in medical science since the middle of the 20th century. The primary function of a prohormone is to enhance the strength of the hormone that already occurs in the body. Prohormones add no hormones whereas steroids add hormones which commonly causes confusion between the two. Examples of natural, human prohormones include proinsulin and pro-opiomelanocortin.

For peptide hormones, the conversion process from prohormone to hormone typically occurs after export to the endoplasmic reticulum and often requires multiple processing enzymes. For example, proinsulin is processed by PC 1/2, PC 3, and carboxypeptidase E to afford insulin.^{[citation needed]} Proamylin, which is cosecreted with proinsulin, requires the above three factors and an amidating monoxygenase.

For small molecule hormones, the conversion is often one step, and is often used to regulate hormone levels.

Prohormones of testosterone and other androgenic steroids

In the last two decades, prohormones have also been used by bodybuilders, athletes, and nonmedical users of anabolic steroids and other hormones to refer to substances that are expected to convert to active hormones in the body. The intent is to provide the benefits of taking an anabolic steroid without the legal risks, and to achieve the hoped-for benefits or advantages without use of anabolic steroids themselves. Many of these compounds are legal to manufacture, sell, possess and ingest eliminating the legal problems associated with schedule III anabolic steroids. The typical definition of "prohormone" includes a steroidal molecule that has the opposite molecular structure to testosterone on either the 3a/b position or the 17b position. Testosterone has a ketone group on the 3 carbon and a hydroxyl on the 17b carbon. A steroid with modifications away from testosterone in one or both of these areas is commonly referred to as a "prohormone". These enzymatic changes occur with the body's bidirectional enzymes.

A typical prohormone is intended to be a precursor of an anabolic steroid like testosterone, which is taken in order to boost the body’s available hormone supply. These precursors are intended to be converted 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.

Prohormones are used mainly by athletes looking to increase size, strength, endurance, reduce recovery time or add lean body mass. They are most often used for increasing muscle mass or reducing body fat levels. Life extension groups are also increasingly using prohormones as a means of hormone replacement therapy, as an alternative to prescription drug use. Additionally there is a movement to use prohormones of androgens to help offset the damaging effects of environmental androgens on the body. Chemical endocrine disruptor agents like bisphenol A are becoming recognized as having the ability to skew the androgen to estrogen ratio. This skewed ratio can have many adverse effects on men, including sexual performance, impotence and other testosterone dependent body functions.

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 anabolic steroids, including gains in muscular strength and hypertrophy. There are currently many companies manufacturing prohormone products for this purpose.

Prohormones have the same side effects as anabolic steroids, and are dependent upon the user as to which side effects one might experience. Some side effects are acne, hair loss, breast tissue enlargement, and prostate swelling however these are specific to each type of prohormone and reports of side effects are usually minimal.

The potential for these side effects does exist, but it can be reduced if one uses proper precautionary measures such as post cycle therapy (PCT).^{[citation needed]} Generally, if a person is genetically predisposed to a side effect it will occur (i.e.: if someone has a history of male pattern baldness in the family, it could be assumed that this could be a side effect experienced if prohormones are used)

On October 22, 2004, President Bush signed into law the Anabolic Steroid Control Act of 2004 (118 Stat. 1661). The bill was written to become effective in 90 days, which was January 20, 2005. This legislation places both anabolic steroids and some prohormones on a list of controlled substances (a new type of "regulatory control").^{[citation needed]} This bans the selling or possessing of only the following prohormones.

Prohormones Added To The List Of Schedule III Anabolic Steroids:

androstanediol—3b,17b-dihydroxy-5a-androstane; and 3a,17b-dihydroxy-5a-androstane;

androstanedione (5a-androstan-3,17-dione);

1-androstenediol (3a,17b-dihydroxy-5a-androst-1-ene);

4-androstenediol (3b,17b-dihydroxy-androst-4-ene); and 5-androstenediol (3b,17b-dihydroxy-androst-5-ene);

1-androstenedione ([5a]-androst-1-en-3,17-dione);

4-androstenedione (androst-4-en-3,17-dione); and 5-androstenedione (androst-5-en-3,17-dione); norandrostenediol—19-nor-4-androstenediol (3b, 17b-dihydroxyestr-4-ene);

19-nor-4-androstenediol (3a, 17b-dihydroxyestr-4-ene);

19-nor-5-androstenediol (3b, 17b-dihydroxyestr-5-ene); and 19-nor-5-androstenediol (3a, 17b-dihydroxyestr-5-ene);

norandrostenedione—19-nor-4-androstenedione (estr-4-en-3,17-dione); and 19-nor-5-androstenedione (estr-5-en-3,17-dione; and any salt, ester, or ether of a drug or substance described in this paragraph

Common types of prohormones prior to 2004 anabolic control act

4-androstenedione

• Converts to: testosterone via 17bHSD
• Characteristics:
  • Research indicates a conversion rate of about 5.9%, which means that of the amount taken orally, 5.9% is converted to testosterone.
  • Relatively high rate of aromatization to estrogens, 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.^{[citation needed]}
  • A recent study looking at the long term effects of androstenedione use in rats for their entire life cycle showed no increase in mortality over a control group, showing that androstenedione and presumably all prohormones without chemical modifications to be reasonably safe.

4-androstenediol (4-AD)

• Converts to: testosterone via 3bHSD
• Characteristics:
  • Conversion rate of about 15.76%, almost triple that of androstenedione, due to utilization of a different enzymatic pathway.

19-norandrostenedione

• Converts to: nortestosterone (also called nandrolone) via 17bHSD
• Characteristics:
  • Only slightly less anabolic than testosterone.
  • Low rate of aromatization to estrogens.
  • Low occurrence of androgenic side effects.^{[citation needed]}

19-norandrostenediol

• Converts to: nortestosterone vis 3bHSD
• Characteristics:
  • Low occurrence of androgenic side effects.

1-androstenediol (1-AD)

• Converts to: 1-testosterone, a 5-alpha reduced 1-ene steroid; 1-testosterone is better (although rarely) described as dihydroboldenone, the 5-alpha reduced version of the naturally occurring steroid boldenone^{[citation needed]}
• Characteristics:
  • Cannot aromatize to estrogen either directly or through any of its metabolic products. However, 1-Testosterone, being a 5-alpha reduced steroid, is highly androgenic; it is very similar to Dihydrotestosterone (DHT). Many side effects associated with excessive levels of DHT, including male pattern baldness, testicular shrinkage, benign prostate hypertrophy and acne can occur with 1-AD usage. (Journal of Organic chem. vol, 27 1962 iss.1)

1,4-androstadienedione (1,4 AD)

• Converts to: boldenone
• Characteristics:
  • High level of oral bioavailability.
  • Low rate of aromatization to estrogens (approximately half that of testosterone).
  • Low occurrence of androgenic side effects.^{[citation needed]}

1-testosterone (1-T)

• Characteristics:
  • similar to testosterone except instead of a 4,5-double bond it has a 1,2-double bond.
  • has about 20% oral bioavailability compared with less than 5% for testosterone
  • non-aromatizing to estrogen or DHT
  • has irritative properties making it too painful to inject, and has extremely bitter taste, making transcutaneous topical solutions the only practical human delivery method. It was commercialized this way in the United States before 2005, when it became illegal together with many other prohormones.
• History: 1-T was discovered in the 1950s, explored as a potential anabolic product by the pharmaceutical company G.D. Searle, but not commercialized at the time due to difficulty in delivery.^{[citation needed]}
• Also considered a steroid