by Bill Roberts - Testosterone, as the natural product drug and one of the most widely used AAS, is the most convenient choice for a reference drug to which all others will be compared.

Particular properties of testosterone that are of note include that it converts enzymatically both to DHT and to estradiol (estrogen). While with normal levels of testosterone these conversions are in fact desirable, with supraphysiological levels caused by drug adminstration they can be undesirable. DHT is at least three times more potent (effective per milligram) than testosterone at the androgen receptor (AR): therefore, in those tissues which convert testosterone to DHT, there is effectively three times as much androgen as elsewhere in the body. Thus, whatever level of androgen is experienced by the muscle tissue is multiplied threefold or more in the skin and in the prostate. This can be excessive. Proscar could be used to keep DHT levels more or less normalized despite heavy testosterone use, however.

Excess conversion to estrogen is also undesirable since it contributes to inhibition of the hypothalamic/pituitary/testicular axis (HPTA), can cause or aggravate gynecomastia, can cause bloating, and can give unfavorable fat pattern distribution. This conversion can be somewhat reduced by use of aromatase inhibitors such as Cytadren, and/or the effects of the estradiol produced may be blocked in many tissues, including the hypothalamus and breast tissue, by Clomid.

Among the most significant differences of synthetic AAS compared to testosterone is that they may avoid either or both of these enzymatic conversions. Another difference results from the fact that not all activity caused by androgens is mediated by the androgen receptor, and not all AAS are comparably effective in these other activities.

Testosterone used alone is capable of giving very effective results, particularly with doses over one gram per week, and can give substantial results with only 500 mg/week. If no other drugs are used, however, side effects such as gynecomastia are fairly likely. Prostate enlargement, worsening of acne, and acceleration of male pattern baldness (for those genetically susceptible to it) are particularly severe because of the effectively-higher androgen levels seen in these tissues as a result of local conversion to the more-potent DHT. Synthetics which do not convert to DHT give only the same effective level of androgen in these tissues as in the body as a whole, rather than effectively three times the level. This is a significant advantage.

A particularly interesting property of testosterone is its low toxicity, exclusive of the above-mentioned side effects. Doses of two grams or four grams per week are hardly unknown in bodybuilding, and are not particularly hard on the liver. No one seems to want to take doses of any other single steroid at comparably-effective doses, and it seems that if one tried, they might be more toxic. E.g., the hepatotoxicity of Winstrol Depot resulting from its 17a -methyl group is not severe at doses of say 350 mg/week, but might well be problematic at a dose of two grams per week – though that is speculation, since no one I have heard of uses such doses of Winstrol. Thus, at the higher dosage regimes testosterone appears to have an advantage in terms of toxicity vs. effectiveness over many of the synthetics. These doses, however, are in the pro bodybuilder range. In the dosage range more appropriate for most individuals, the reverse is often the case.

Injectable testosterone esters commonly used for testosterone therapy:

• Testosterone Enanthate: Chemical Formula C7H14O2
  
  Testosterone enanthate is one of the main forms of testosterone prescribed in the United States. It is a slow-acting ester with a release time between 8-10 days. The name-brand of T-enanthate available in the United States is called "Delatestryl," which is suspended in sesame oil. Testosterone enanthate is typically injected anywhere between once every week to once every three weeks.
  
  Download Delatestryl Package Insert

• Testosterone Cypionate: Chemical Formula C8H14O2
  
  Testosterone cypionate is the other main injectable form of testosterone prescribed in the United States. It is a slow-acting ester with a release time between 8-10 days, similar to that of enanthate. The name-brand of testosterone cypionate available in the United States is called "Depo-Testosterone," which is suspended in cottonseed oil. Testosterone cypionate is typically injected anywhere between once every week to once every three weeks.
  
  Download Depo-Testosterone Package Insert

• Sustanon 250
  
  "Sustanon" is the brand name for a blend of four testosterone esters: testosterone propionate (C3H6O2), testosterone phenylpropionate (C9H10O2), testosterone isocaproate (C6H12O2), and testosterone decanoate (C10H20O2). It features both fast-acting and slow-acting esters, and can be injected anywhere from once every week to once every four weeks. It is prescribed outside of the United States.

• Testosterone Propionate: Chemical Formula C3H6O2
  
  Testosterone propionate is a fast-acting ester with a release time of 3-4 days. To keep blood levels from fluctuating greatly, propionate is usually injected between one to three times a week. Some users also report that propionate is a more painful injection, with swelling and noticeable pain around the injection site. Brand names of testosterone propionate include "Testovis" and "Virormone."

• Testosterone Phenylpropionate: Chemical Formula C9H10O2
  
  Testosterone phenylpropionate is a slow-acting ester, with a release time of 1-3 weeks. A popular name brand for T-phenylpropionate is "Testolent." Testosterone phenylpropionate is also one of the components of Sustanon and Omnadren.

• Omnadren
  
  "Omnadren" is the brand name for a blend of four testosterone esters: testosterone propionate (C3H6O2), testosterone phenylpropionate (C9H10O2), testosterone isocaproate (C6H12O2), and testosterone decanoate (C10H20O2). In the past, Omnadren consisted of a blend of different esters, but now is essentially the same formula as Sustanon, mentioned above. It features both fast-acting and slow-acting esters, and can be injected anywhere from once every week to once every four weeks. It is sometimes prescribed in parts of Europe.

• Aqueous Testosterone Suspension
  
  In the United States, injectable aqueous (non-esterified) testosterone is available, but it is very short-acting (it is completely released in the system within a matter of hours). The brand name for aqueous testosterone suspension is "Aquaviron."

TRANSDERMAL TESTOSTERONE

Testosterone Patches

• Androderm
  
  Androderm patches come in two doses: 2.5 mg/patch and 5.0 mg/patch. The actual amount of testosterone in the 2.5 mg patch is 12.2 mg, and the actual amount in the 5.0 mg patch is 24.3 mg. The reason is that much of the testosterone in the patch will not manage to get into the system. So, for example, the aim of the 2.5 mg patch is to get about 2.5 mg successfully into the bloodstream per day. Therefore, it is possible to absorb slightly more or slightly less than the 2.5 mg of the patch's ideal dosage (the same reasoning, of course, applies to the 5.0 mg patch as well).
  
  Androderm patches are usually applied on the back, abdomen, thighs, or upper arms. Because the active area of the patch is covered, the wearer does not have to worry about skin contact with a partner. Dosages will vary between 2.5 mg - 10 mg daily, by applying a single patch or combination of patches.

  Download Androderm Package Insert
   

• Testoderm TTS
  
  There are two types of Testoderm patches: one is intended for scrotal application, and one for application on other areas of the body. Testoderm TTS refers to the non-scrotal version of the patch.
  
  Testoderm TTS patches come in two doses: 4.0 mg/patch and 6.0 mg/patch. As with Androderm, the actual amount of testosterone in these patches is greater than the listed dose. The reason is the same as explained above in the Androderm section.
  
  Testoderm TTS patches are usually applied on the back, abdomen, thighs, or upper arms. Because the active area of the patch is covered, the wearer does not have to worry about skin contact with a partner. Dosages will vary between 4.0 mg - 10 mg daily, by applying a single patch or combination of patches.

Testosterone Gels

• Androgel
  
  Androgel is a clear, alcohol-based gel that contains 1% non-esterified testosterone. It is very fast-acting once it has been absorbed by the skin, and so must be reapplied at 1-2 times daily to maintain T levels. It is available in either unit-dose packets or multiple-dose pumps. The unit dose packets contain either 25 mg or 50 mg of testosterone. Approximately 10% of the applied testosterone from the packets is absorbed into the system, resulting in an effective dose of 2.5 mg or 5.0 mg, respectively.
  
  Androgel should be applied to clean, dry skin and should not be applied to the genital area. Application sites should be allowed to dry for a few minutes prior to dressing. Hands should be washed thoroughly with soap and water after application.
  
  In order to prevent transfer to another person, clothing should be worn to cover the application sites. If direct skin-to-skin contact with another person is anticipated, the application sites should be washed thoroughly with soap and water. Users should wait at least 2 hours after applying before showering or swimming; for optimal absorption, it may be best to wait 5-6 hours.
  
  Download AndroGel Package Insert
   
• Testim
  
  Testim, like Androgel, is a clear, alcohol-based gel that contains 1% non-esterified testosterone. It is very fast-acting once it has been absorbed by the skin, and so must be reapplied at 1-2 times daily to maintain T levels. It is available in 5.0g unit-dose tubes. A 5.0g unit dose tube contains 50 mg of testosterone. Approximately 10% of the applied testosterone from the tube is absorbed into the system, resulting in an effective dose of 5.0 mg.
  
  Testim should be applied to clean, dry skin-- preferably to the shoulders and/or upper arms. It should not be applied to the genitals or to the abdomen. Application sites should be allowed to dry for a few minutes prior to dressing. Hands should be washed thoroughly with soap and water after application.
  
  In order to prevent transfer to another person, clothing should be worn to cover the application sites. If direct skin-to-skin contact with another person is anticipated, the application sites should be washed thoroughly with soap and water. Users should wait at least 2 hours after applying before showering or swimming; for optimal absorption, it may be best to wait 5-6 hours.

ORAL TESTOSTERONE

• Methyltestosterone (C-17 Alpha Alkylated Testosterone)
  
  Methyltestosterone is one of the earliest available oral testosterones. Its chemical structure is the hormone testosterone with an added methyl group at the c-17 alpha position of the molecule. Brand names include "Metesto," "Methitest," "Testred," "Oreton Methyl," and "Android."

• Testosterone Undecanoate
  
  Testosterone undecanoate is not a c-17 alpha alkylated hormone. Therefore, it is considered a safer oral form of testosterone. Additionally, it is absorbed through the small intestine into the lymphatic system, posing less burden on the liver. Brand names for testosterone undecanoate include "Andriol," "Androxon," "Understor," "Restandol," and "Restinsol." It is not available in the United States.
  
  One disadvantage of orally administered undecanoate is that it is eliminated from the body very quickly, usually in 3-4 hours. Thus, frequent administration is necessary-- usually between 3-6 capsules a day. This can prove to be quite expensive when compared to injectable testosterone.
  
  Download Andriol Package Insert

BUCCAL TESTOSTERONE

• Buccal
  
  In 2003, the FDA approved a sustained-release buccal testosterone tablet called "Striant." It acts by adhering to the buccal mucosa (the small depression in the mouth where the gum meets the upper lip above the incisor teeth). Once applied, the tablet softens and delivers testosterone through the buccal mucosa, where it is then absorbed directly into the bloodstream, bypassing the gastrointestinal system and liver.
  
  The recommended dosage for Striant is to replace the tablet about every 12 hours, though a different dosing schedule or number of tablets might be required depending on the needs of the patient.
  
  Download Striant Package Insert

SUBCUTANEOUS TESTOSTERONE PELLET

• Another relatively new form of testosterone delivery is via a pellet of pure, crystalline testosterone implanted beneath the skin. The pellets are about the size of a grain of rice, and are typically placed in the buttocks or abdomen. The insertion of the pellets is a quick procedure, usually done under local anesthesia. Pellets are usually replaced after 3-4 months. "Testopel" is a brand name for testosterone pellets in the United States.
  
  A 200 mg testosterone pellet releases testosterone at a steady rate of 1-3 mg per day. Several pellets can be inserted at the same time to increase dosage.
  
  Some users have reported problems with the pellets working their way out from under the skin.

Trivial name	Testosterone [USAN:INN] (base)
Chemical name	17ß-hydroxyandrost-4-en-3-one
Systematic Name	(8S,9S,10R,13S,14S,17S)-17-hydroxy-10,13-dimethyl-1,2,6,7,8,9,11,12,14,15,16,17-dodecahydrocyclopenta[a]phenanthren-3-one
Index name	Androst-4-en-17beta-ol-3-one
CAS number	58-22-0
Empirical formula	C19-H28-O2
Merck Index Number	Merck 11, 9109
Molecular weight	288.424 g/mol
Pregnancy category	X
Legal status	Prescription only (US); DEA Schedule III (US)
Routes of administration	Transdermal

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