4-androstenediol (4-AD) is an effective prohormone to testosterone. Naturally found in several tissues of the body, 4-AD is converted to testosterone via the enzyme 3beta-HSD. 4-AD converts to testosterone at a significantly higher rate than other commercially available prohormones (such as androstenedione), and also does not have the weakness of conversion to estrogen and/or DHT prior to conversion to testosterone. This makes 4-AD the best testosterone prohormone on the market.

Since testosterone is the target hormone, the effects of 4-AD supplementation will be consistent with an increase in testosterone levels. Since testosterone converts to both estrogen and DHT, both androgenic and estrogenic side effects can be expected. Although not commonly used as a standalone because of these side effects, 4-AD is used in most prohormone stacks. Since exogenous steroids shut down natural production of testosterone via negative feedback, 4-AD can help reduce the side effects of low testosterone and low estrogen experienced with many substances (such as loss of libido) while also providing additional anabolic benefit. 19-nordiol and 4-AD and 1-AD or 1-test and 4-AD are both common stacks. 4-AD is also recommended to counteract some of the side effects of methyl-1-test.

4-AD is best used as a transdermal, as it has low oral bioavailability. 300-600 mg is the commonly used transdermal dosage when stacking, while higher doses (700-1000 mg) are used as a standalone. Oral 4-AD doses, even when stacking, may go up to as much as 1.5 g daily, although most use 600-900 mg. This is generally spread out over 3-4 doses. Sublingual 4-AD can also be used as a preworkout stimulant.

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