Despite a dearth of information on their effects, supplementation with andro-compounds has become widespread. Unlike synthetic anabolic-androgenic steroids, these precursor androgens are produced endogenously by adrenal, gonadal, and peripheral steroidogenic pathways as part of the normal sexual and reproductive hormonal milieu. It has been suggested that peripheral enzymatic conversion of these pro hormones to testosterone (via ingestion of androstenedione/diol) or nor-testosterone (via ingestion of 19-nor-androstenedione/diol) might lead to anabolic and/or ergogenic effects. Beyond the narrow scope of performance enhancement, it has also been alleged that supplementation with prohormones might be useful in correcting the gradual decline in testosterone and DHEA concentrations that accompany the aging process. None of these claims have been proven or adequately examined to date.The biosynthesis of testosterone from the -dione and -diol prohormones is controlled by the ubiquitous enzymes 17- and 3-beta-hydroxysteroid dehydrogenase, respectively. Because these enzymes exist as a family of multiple isozymes, each with a specific oxidative/ reductive activity, substrate specificity, and cell-specific expression, prohormone ingestion might, either directly or indirectly, affect the formation of a number of sex steroids other than testosterone (e.g., DHEA, estrone, estradiol, etc.). Initial research in men using single and repeated 100-mg oral doses of androstenedione reported no effect on testosterone concentrations or rates of muscle protein synthesis. Subsequent studies have indicated that oral doses of 200-300 mg are capable of increasing serum testosterone modestly, i.e., up to 34% when mean-area-under-the-curve values are compared. 
A relatively consistent finding in most studies thus far, however, has been increases in serum estrone and estradiol. These aforementioned results are not surprising given the known (poor) bioavailability of orally administered androgens and the high aromatase activity of hepatic tissue. Collectively, recent data from our research group and others examining the acute and chronic effects of oral, sublingual, and transbuccal prohormone administration in men suggest that -
1) Any increase in serum testosterone concentrations from acute, oral androstenedione administration are overÂshadowed by larger increases in circulating estrogen
2) Daily ingestion of androstenedione during intense resistance training does not lead to greater gains in strength or hypertrophy, at least at dosages between 100-300 mg/day
3) Short-term sublingual and transbuccal administration of androstenediol, on the other hand, may significantly elevate serum testosterone without effects on estradiol concentrations or lipid, renal, and hepatic profiles.
Given the popularity of prohormones and the wide array of clinical effects that androgens may have on health (e.g., alterations in blood lipids, cardiovascular disease risk, bone density, immunocompetence, libido, visceral adiposity, insulin sensitivity, etc.) more research in this area is needed. Admittedly, this will be a complex task because of the numerous interrelated factors that are known to influence individual responses to androgen administration, most notably the genetic polymorphisms of the androgen receptor and potential hormonal interconversions at the paracrine level. Nevertheless, appropriately controlled human trials involving large sample sizes, dose response, duration of use issues, and documentation of side effects must be conducted before the risk-to-benefit ratio of pro hormone use can be accurately determined.
Tags:anabolic androgenic steroids, Androgens, androstenedione, dhea, enzymes, ergogenic effects, muscle protein synthesis, prohormones, serum testosterone ubiquitous
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