Hydroxytestosterone is an anabolic steroid that is, as its name would indicate, a close structural relative of the primary androgen testosterone. Specifically, it is testosterone with an added 4-hydroxl group, an alteration that makes this an extremely interesting steroid. In action it is only moderately anabolic and androgenic, ultimately bearing little resemblance to the androgen (testosterone) that it is so closely related to on a molecular level. Hydroxytestosterone was originally developed by the pharmaceutical manufacturing giant Searle back in the 1950's, however, it never did make it to the shelf as a commercial prescription steroid product. Despite having several unique and favorable characteristics, it lay lost in the research books for decades, the manufacturer and patent holder probably finding little financial incentive to market it next to the many other anabolic agents available. This steroid was sold legally as a sports supplement in the U.S. until January 2005, when it became a Schedule III controlled substance.
In regards to structure, the first thing we can point out about hydroxytestosterone Is that the 4-hydroxyl group prevents aromatization. As such, this steroid is totally incapable of converting to estrogen. Not only that, this alteration also gives hydroxytestosterone strong aromatase inhibiting activities. You see, hydroxytestosterone differs from the suicide aromatase inhibitor formestane (4-hydroxyandrostenedione) only in that it is the active form of the steroid (17-beta hydroxysteroid) instead of the inactive dione (17-ketosteroid). Both types of steroid hormone will interact with the aromatase enzyme. In a clinical setting, formestane would be the obvious choice,as you would usually want to lower estrogen without presenting the often-female patients with unwanted androgenic side effects. So I can understand why hydroxytestosterone was never explored for this use. But this active steroid is still very much a potent aromatase inhibitor. This all means that with hydroxytestosterone, there is not only no need to worry about estrogenic side effects such as gynecomastia, water retention, or fat buildup, but that the agent can even be used to counter such side effects caused by the aromatization of other steroid compounds. It is therefore a dual-purpose anabolic/aromatase-inhibiting agent.
As with all naturally occurring (non-methylated) steroid hormones, hydroxytestosterone is not intrinsically very orally active. This has been the problem with the "legal steroid/prohormone" market from the beginning. These natural steroidal hormones work, some of them extremely well, if you can get them into your body first. As you may know, I found and publicized the research showing the natural occurrence of 4-hydroxysteroids like hydroxytestosterone, and eventually sold it through my supplement company (Molecular Nutrition) as an oil-solubilized softgel (as hydroxytestosterone hexyldecanoate). This is about the only type of oral product I would have recommended. Otherwise, it could have been used in a transdermal formula, or homebrewed injection.The latter would be the preferred in terms of bioavailability, not really for safety. In any event, the product is now illegal to sell in the U.S., so any version produced now would have to be of black market or international pharmaceutical origin.
Effective daily doses for most male bodybuilders would be in that range of 200-400mg per week by injection, or 100-300mg if taking an oil-solubilized oral product. Maximum aromatase inhibition is reached by 250mg per week when given by injection, or 100-200mg per day when taking oral softgels.One could obviously keep the doses limited to this range if estrogen minimization is the main focus of use. Hydroxytestosterone and formestane may not be quite as potent as the selective third generation non-steroidal aromatase inhibitors Arimidex or Femara in terms of estrogen minimization, but they do seem to do a much better job here than the "standard issue" estrogen receptor antagonists Nolvadex and Clomid (especially when it comes to shedding water and producing the tight "high androgen" look). As with all effective aromatase inhibitors, its estrogen lowering action is likely to be accompanied by a negative lowering of HDL (good) cholesterol levels. For this reason hydroxytestosterone should never be used for long periods of time, and regular doctor's checkups are recommended during use.