Androstenedione

Androstenedione (also known as 4-androstenedione) is a 19-carbon steroid hormone produced in the adrenal glands and the gonads as an intermediate step in the biochemical pathway that produces the androgen testosterone and the estrogens estrone and estradiol.

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Synthesis

Androstenedione is the common precursor of male and female sex hormones. Some androstenedione is also secreted into the plasma, and may be converted in peripheral tissues to testosterone and estrogens.

Androstenedione originates either from the conversion of dehydroepiandrosterone or from 17-hydroxyprogesterone. Conversion of 17-hydroxyprogesterone to androstenedione requires 17,20 lyase. 17-hydroxyprogesterone, on the other hand, requires 17,20 lyase for its synthesis. Thus, both reactions that produce androstenedione directly or indirectly depend on 17,20 lyase.

Androstenedione is further converted to either testosterone or estrogen. Conversion of androstenedione to testosterone requires the enzyme 17β-hydroxysteroid dehydrogenase, while conversion of androstenedione to estrogen (e.g. estrone and estradiol requires the enzyme aromatase.

The production of adrenal androstenedione is governed by ACTH, whereas production of gonadal androstenedione is under control by gonadotropins. In premenopausal women, the adrenal glands and ovaries each produce about half of the total androstendione (about 3 mg/day). After menopause, androstenedione production is about halved, primarily due to the reduction of the steroid secreted by the ovary. Nevertheless, androstenedione is the principal steroid produced by the postmenopausal ovary.

Endocrine function

In females, androstenedione is released into the blood by theca cells. The function of this is to provide androstenedione substrate for estrogen production in granulosa cells, since these haven't got the 17,20 lyase required for androstenedione. The other way around, theca cells haven't got the aromatase required to make estrogens themselves. Thus, theca cells and granulosa cells work together to form estrogen^[1] .

Androstenedione as a supplement

Androstenedione was manufactured as a dietary supplement, often called andro (or andros) for short. Andro was in common use in Major League Baseball throughout the 1990s by record-breaking sluggers like Mark McGwire, but it is unknown (and unknowable) to what extent andro was responsible for McGwire's exceptional performance. The supplement is banned by the World Anti-Doping Agency, and hence from the Olympic Games.

On March 12, 2004, the Anabolic Steroid Control Act of 2004 was introduced into the United States Senate. It amended the Controlled Substance Act to place both anabolic steroids and prohormones on a list of controlled substances, making possession of the banned substances a federal crime. The law took effect on January 20, 2005.

On April 11, 2004, the United States Food and Drug Administration banned the sale of Andro, citing that the drug poses significant health risks commonly associated with steroids.

Conversion to estrone

Because androstenedione is converted in part to estrogens, persons taking this supplement may have estrogenic side-effects. A visible problem could be gynecomastia (formation of breast tissue) in males.

Additional images

References

1. ^ Medical Physiology, Boron & Boulpaep, ISBN 1-4160-2328-3, Elsevier Saunders 2005. Updated edition. Page 1155