Androstenedione (ASD)

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. 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.

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 cells lack 17,20 lyase required for androstenedione. Similarly, theca cells lack the enzyme aromatase required to make estrogens themselves. Thus, theca cells and granulosa cells work together to form estrogen.