17-Andro is also known as Androstenedione, or 4-androstenedione (abbreviated as A4 or Δ4-dione), also known as androst-4-ene-3,17-dione, is an endogenous androgen steroid hormone and intermediate in the biosynthesis of estrone and of testosterone from dehydroepiandrosterone (DHEA). It is closely related to androstenediol (androst-5-ene-3β,17β-diol).
Androstenedione can be biosynthesized in one of two ways. The primary pathway involves conversion of 17α-hydroxypregnenolone to DHEA by way of 17,20-lyase, with subsequent conversion of DHEA to androstenedione via the enzyme 3β-hydroxysteroid dehydrogenase. The secondary pathway involves conversion of 17α-hydroxyprogesterone, most often a precursor to cortisol, to androstenedione directly by way of 17,20-lyase. Thus, 17,20-lyase is required for the synthesis of androstenedione, whether immediately or one step removed.
Androstenedione is produced in the adrenal glands and the gonads. The production of adrenal androstenedione is governed by adrenocorticotrophic hormone (ACTH), whereas production of gonadal androstenedione is under control by the gonadotropins. In premenopausal women, the adrenal glands and ovaries each produce about half of the total androstenedione (about 3 mg/day). After menopause, androstenedione production is about halved, due primarily to the reduction of the steroid secreted by the ovary. Nevertheless, androstenedione is the principal steroid produced by the postmenopausal ovary.
Some androstenedione is also secreted into the plasma, and may be converted in peripheral tissues to testosterone and estrogens.
Leder, et al. (2000) demonstrated a clinical outlook on Androstenedione: “This study shows that oral androstenedione administration increases serum testosterone, androstenedione, estradiol, and estrone concentrations in healthy men. Few studies have examined the effects of oral androstenedione administration on testosterone production in humans. A 100-mg dose of androstenedione increased testosterone concentrations in 2 women. In a recent study, in which androstenedione was administered either as a single 100-mg dose or as 100 mg 3 times daily to healthy men, testosterone concentrations did not increase, although estrogen levels did. Our data confirm that individual 100-mg doses of androstenedione are insufficient to increase testosterone concentrations in healthy men. However, our data also demonstrate that a higher dose does increase serum testosterone concentrations.
The enzyme that converts androstenedione to testosterone, 17β-hydroxysteroid dehydrogenase, and aromatase, the enzyme complex that converts androstenedione and testosterone to estrone and estradiol, are expressed in many human tissues including skeletal muscle and fat. Thus, it is possible that increases in local tissue levels of testosterone, estrone, or estradiol are even greater than the increases in their circulating concentrations.
That oral androstenedione administration increases serum testosterone levels suggests that it could have androgenic or anabolic effects. High doses of testosterone increase muscle size and strength in healthy men. It is unclear if smaller increases in serum testosterone also have anabolic effects. Muscle size and strength did not change when 100 mg of androstenedione was administered 3 times daily to healthy men without prior weight-lifting experience.6 As this dose was not sufficient to raise testosterone levels, it remains unknown if doses of androstenedione that increase testosterone levels would have significant effects on muscle size and function. Finally, because androstenedione itself is a weakly androgenic steroid, increases in androstenedione itself could have anabolic effects.
While testosterone levels increased in the subjects receiving the 300-mg/d dosage, levels returned to normal by the following day. This is expected given that the half-life of testosterone in circulation is 60 to 80 minutes. Because many users probably take much higher and more frequent doses of androstenedione, it is likely that some individuals may experience sustained and larger increases in testosterone levels compared with those observed in the present study. Additionally, there was considerable variability in changes of circulating sex steroid concentrations among the subjects. Because some individuals achieved much higher circulating testosterone and estradiol concentrations than others (often above the normal range), there may be subsets of men prone to develop androgenic or estrogenic responses to androstenedione administration.”
Because of the expected increase in estrogens, users should additionally include an aromatase inhibitor or selective estrogen receptor modulator (SERM) as part of a complete cycle with 17-Andro, to obtain maximum benefit.
To truly maximize the benefit of 17-Andro, be sure to stay hydrated, sleep 7-9 hours per night, resistance train regularly, and keep up with your cardiovascular training as well!