Androstenedione RIA

Intended Use

Radioimmunoassay for the in vitro quantitative measurement of human 4-Androsten-3, 17-Dione (Androstenedione) in serum and plasma.

This assay is intended for in vitro diagnostic use only.

Biological Activity

4-Androsten-3, 17-dione (Androstenedione) is a C19 steroid. It is produced in the adrenal gland and gonads. Androstenedione is an immediate precursor to both testosterone and estrone, both of which may be subsequently converted to estradiol. Due to the presence of a 17-oxo (rather than hydroxyl) group, Androstenedione has relatively weak androgenic activity, estimated at ≤ 20 % of testosterone. Although it is a weak androgen, serum Androstenedione levels may exceed testosterone in both normal and disease states, Androstenedione secretion and production rates exceed those of testosterone in women, and significant extraadrenal conversion of Androstenedione to testosterone occurs. Furthermore, the affinity of sex hormonebinding globulin for Androstenedione is much less than for testosterone or estradiol (1 – 3).

The physiologic role of Androstenedione is not well defined. Serum Androstenedione levels are high in fetal and neonatal serum, decrease during childhood, and increase during puberty. In normal pubertal and adult men, the major portion of Androstenedione is derived from the testis, either directly or from conversion of testosterone, while in normal adult women, essentially equivalent amounts of Androstenedione are produced by the adrenal gland and ovary (2,3). Increased Androstenedione levels may play a role in the development of secondary sexual hair during adrenarche. Serum Androstenedione levels show significant diurnal variation dependent on the secretion of ACTH. Ovarian Androstenedione production is stimulated by luteinizing hormone, and serum Androstenedione levels vary with the menstrual cycle (3). Adrenal Androstenedione production gradually declines with advanced age in both men and women. In addition, ovarian Androstenedione production decreases after menopause(3).

Clinical Applications

Measurement of Androstenedione provides a useful marker of androgen biosynthesis: Elevated Androstenedione levels have been demonstrated in virilizing congenital adrenal hyperplasia; additionally Androstenedione levels may have advantages over 17-hydroxy-progesterone levels in monitoring treatment of this condition, e.g. less marked diurnal variation and less suppression after brief glucocorticoid exposure (4). Serum Androstenedione levels are also increased in polycystic ovary syndrome, ovarian stromal hyperthecosis, 3b-hydroxysteroid dehydrogenase deficiency, and other causes of hirsutism in women (3,6 & 7). By definition, Androstenedione levels are normal in idiopathic hirsutism. Elevated serum Androstenedione levels may also occur in adrenal and ovarian virilizing tumors (3). In a prospective study of over 1000 men, a dose-response relationship of androstenedione and prostate cancer risk was demonstrated (5); additional studies will be needed to confirm these findings.

For concrete data please consult the Instruction for Use in the download box on the top right side.