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. 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. 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 anabolic 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 putative 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. However, in USA, since prohormones are now listed alongside anabolic steroids themselves, they are classified as illegal and subject to the much tighter regulatory requirements of the Food and Drug Administration (FDA) which apply to prescription hormones. The FDA moved to halt sales of androstenedione, a dietary supplement marketed as a muscle enhancer that officials said can stunt growth in children's penises and cause problematic sexual changes in adults. "This is a critical part of the FDA's broad crackdown on unsafe dietary supplements," said Dr. Mark McClellan, the FDA commissioner, at a news conference. "While andro products may seem to have short-term benefits, the science shows that these same properties create real and significant health risks. "
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.
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.
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). 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 22nd, 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 prohormones on a list of controlled substances (a new type of "regulatory control"). This bans the selling or possessing of all prohormones.
Included here are some of the most common questions asked about prohormones. This has been compiled into information based on some scientific studies, but mostly from user feedback after years of success using prohormones. Please keep in mind that this document might have some errors and you will need to do much more reading before you decide whether or not use prohormones.
What are prohormones ?
Prohormones are synthetically manufactured compounds which convert to anabolic hormones via enzymes in the liver; hormone precursors. They are commonly abbreviated as PHs.
What are they used for ?
Prohormones are used 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 bodyfat levels. Life extension groups are also increasingly using prohormones as a means of hormone replacement therapy, as an alternative to prescription drug use.
Do they have side effects?
Yes. Prohormones can have the same side effects as anabolic steroids, and are dependant upon the user as to which side effects one might experience. Some side effects are acne, hair loss, breast tissue enlargement, and prostate swelling. The potential for these side effects does exist, but it can be reduced if one uses proper precautionary measures (see below). 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 certain prohormones are used)
Which prohormones convert to which compounds?
Here is a list
How do prohormones work ?
Basically, when they are administered into the system, they are broken down in the liver and converted to their target hormone via certain enzymes. There have been a number of quotes describing how much of the hormone is converted, but there is no definitive answer as to how much of the prohormone is converted into its target active. Once a certain amount is created, the enzymes used for conversion become saturated and no more can be converted. This is true with all the compounds, except for 1-testosterone which really isn’t a prohormone.
What do the target hormones do ?
Each hormone works in different ways once it is converted, but essentially it attaches to an androgen receptor in the cells of your body. This in turn increases nitrogen retention and protein synthesis, meaning that your body is in a constant anabolic state (assuming you are continuously supplying your body with the hormone). Here is a brief description of each hormone and what it does.
Testosterone is the primary male hormone responsible for development of the sex organs and muscle growth. Testosterone is both anabolic and androgenic—anabolic meaning it causes muscle growth and androgenic meaning that it causes development of secondary sex characteristics. Testosterone converts to both DHT and estrogen in its parent form. Testosterone is often the primary hormone used on a cycle of steroids. It is a mass builder, and will often help with unwanted androgenic side effects of other steroids. Although conversion to estrogen can cause many unwanted side effects on its own, testosterone should generally be the base to any cycle.
Nandrolone is an anabolic hormone, with not as much androgenic potential. It attaches to the androgen receptor with greater affinity than testosterone, but can cause a loss of libido and generally stays active in the system much longer than does testosterone. This is the “safest” choice for users who want to avoid most common side effects.
DHT (dihydrotestosterone) is the primary androgenic hormone in the body. It is responsible for increases in strength, as well as most of the unwanted side effects common with steroids. DHT is converted from testosterone via the 5 alpha reductase enzyme. DHT receptors are high in the scale, skin and prostate; high DTH levels are the most common cause of prostate swelling, acne, and male pattern baldness.
Boldenone is a veterinary hormone, which is commercially sold as Equipoise. Equipoise is known as an alternative to nandrolone when using steroids. It provides an increase in appetite, with some fat burning potential. Boldenone converts to estrogen at about half the rate of testosterone. Those who are looking to avoid some of the stronger androgenic side effects also commonly use it. 1-testosterone is the 5 alpha reduced version of Boldenone.
How do I take prohormones ?
There are three common routes of administration for prohormones. These are usually based on their efficacy (i.e. how much is absorbed). Since the liver and stomach lining breaks down prohormones rather efficiently, taking them orally is the poorest route of administration. Most users prefer transdermal (topical) administration. When taken this way, you apply it to your skin and it will continue being absorbed over a period of 12 hours or so. Cyclodextrins or sublingual methods are also commonly used, which is where the prohormones are dissolved under the tongue. This also has a high level of absorption and works well. There are also some products on the market which are sold as “intraoral” or “intranasal”. These are meant to be sprayed into the nostril prior to your workout, and are generally only meant as preworkout boosts, not for a cycle of prohormones.
Some manufactures have started selling prohormones in oral form with an ester attached. This, in theory, will allow it to be slowly absorbed for many hours similar to the other methods, but to my knowledge, there have been no studies demonstrating that this method increases bioavailability.
What is a cycle? What does stacking mean ?
A cycle is generally used to describe a length of time and common dosage when taking prohormones. Stacking means taking more than one prohormone at a time to increase gains or reduce side effects. Common cycle lengths are 2 weeks, 4 weeks, 6 weeks, and 8 weeks. I recommend 4 week cycles, which seem to give the most gains with fewer sides. I would not recommend going beyond 8 weeks.