Androstenedione Update


Androstenedione, a precursor to testosterone, is normally produced by the adrenal gland and testes and is converted to testosterone through the action of 17 beta-hydroxysteroid dehydrogenase, which is found in most body tissues.( 1) Androstenedione is also produced by some plants and has recently been marketed as a "natural anabolic," a product which increases blood testosterone concentrations.

The conversion of androstenedione and testosterone to other androgens (male hormones) and estrogens (female hormones) is complex. As well as being a precursor of testosterone, androstenedione can be directly converted into estrogen.( 2, 3) Since testosterone is also converted into estradiol,( 3) it is also possible that the increased production of testosterone by administration of androstenedione could result in increased estrogen levels.

To date only one study has investigated the effect of oral androstenedione administration on blood testosterone concentration.( 4) These authors observed four-fold and seven-fold increases in blood testosterone in 2 healthy women after a single dose of 100 mg of androstenedione. The effect on testosterone levels in healthy men was unknown.

A study just released in the June 2, 1999 Journal of the American Medical Association has given us some answers.( 5) The authors took 30 healthy young men, aged between 19 and 29 years with normal testosterone levels who were not taking any nutritional supplements prior to the study and were not currently engaged in a resistance-training program. This was an eight-week randomized controlled trial.

Results showed that testosterone concentrations were not affected by short or long-term androstenedione administration. But serum estradiol (estrogen) concentration was higher in the androstenedione group compared with the pre-supplemented values. Serum estrone (estrogen) concentration was significantly higher than compared with baseline levels. There was no difference between the androstenedione group and placebo group in knee extension strength, in muscle fiber increase, in lean body mass or in decrease in fat mass. But HDL cholesterol (the good cholesterol) was lowered and remained low even after 8 weeks of training and supplementation.

The authors concluded that androstenedione supplementation does not increase serum testosterone concentrations or enhance skeletal muscle when weight training in normal men, and may even result in adverse health consequences. This just confirms what we have already told you (see Vol. 2, No. 5 of the COLGAN Chronicles).

(1.) Horton R, Tait JF. Androstenedione production and interconversion rates measured in peripheral blood and studies on the possible site of its conversion to testosterone. J Clin Invest, 1966;45:301-313.

(2.) MacDonald PC, Rombaut RP, Siiteri PK. Plasma precursors of estrogen l. J Clin Endocrinol Metab, 1967;27: 1103-1111.

(3.) Longcope C, Kato R, Horton R. Conversion of blood androgens to estrogens in normal adult men and women. J Clin Invest, 1969;48: 2191-2201.

(4.) Mahesh VB, Greenblatt RB. The in-vivo conversion of dehydroepiandosterone and androstenedione to testosterone in the human. Acta Endocrinol, 1962;41:400-406.

(5.) King DS, et al. Effect of oral androstenedione on serum testosterone and adaptations to resistance training in young men. J Amer Med Assoc, 1999;281:2020-2028.

Colgan Chronicles.

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