1-Testosterone (17beta-hydroxy-5alpha-androst-1-en-3-one) and 1-AD (1-androstenediol, 1-androstene-3beta, 17beta-diol) are probably the two most effective muscle building supplements presently on the market. 1-testosterone is a steroid that is closely chemically related to testosterone; it has a double bond at the 1 position whereas testosterone has a double bond at the 4 position. 1-AD is a 1-testosterone prohormone that is converted to 1-testosterone by the enzyme 17beta-hydroxysteroid dehydrogenase. Unlike most other prohormones which are readily deactivated in the liver, 1-AD has significant oral activity.

The strong anabolic properties of 1-testosterone have been established in the literature. Research conducted in the 60's found that 1-testosterone had a myotrophic (anabolic) potency of 200 as compared to 26 for testosterone, making it over 7 times as anabolic. This was done using the rat levator ani assay, which is commonly used to test the anabolic potency of steroids. In addition to this, 1-testosterone and 1-AD are both unable to aromatize to estrogen. Hence these substances cause very significant increases in muscle size and strength with about the androgenic potential of testosterone and almost no estrogenic side effects (water retention, fat gain, gynecomastia).

However, 1-testosterone use is not without side effects. The side effects that can be primarily expected from 1-testosterone are androgenic, similar to the side effects of DHT prohormones but not as severe. These include hair loss, acne, and an increased risk of benign prostate hypertrophy (BPH) (although there is much debate concerning the latter subject). Finasteride (********, proscar) cannot be expected to reduce these side effects, as 1-testosterone converts to DHT through a pathway other than 5alpha-reduction. 1-testosterone causes prostate growth in castrated rats equal to that of testosterone; unfortunately this is not a good model for BPH. Those wishing to avoid androgenic side effects should steer clear of 1-AD and 1-testosterone and instead opt for a 19-nor prohormone.

1-AD is used orally, with a low dose being 200-300 mg daily and 600-900 mg daily being commonly utilized (women, should they choose to use 1-AD, should not use a dose higher than 100 mg daily). Dosages as high as 1200-1500 mg daily are not unheard of. 1-testosterone is not considered to be very effective when orally administered, and is most commonly used transdermally at 200-400 mg daily with some going as high as 600 mg. Cycle length for both of these substances is usually 4-8 weeks, although some see good results from 2 week cycles of 1-testosterone. They are most commonly stacked with 4-AD, which can reduce or reverse common side effects such as lethargy and reduced libido. This stack is especially ideal during bulking; during cutting periods, lower doses of 4-AD should be utilized if this stack is chosen. 1-testosterone and 1,4-androstenedione can also be stacked during cutting periods. It is not a good idea to stack these products with DHT precursors (to avoid excessive androgenic side effects) or 19-nor prohormones (as this would cause a significant reduction in libido).