Androstenedione, ACTH Stimulation

The Androstenedione, ACTH Stimulation test is used to evaluate virilizing disorders, including polycystic ovary syndrome, Cushing syndrome, congenital adrenal hyperplasia, and androgen-producing neoplasms of the ovary, testis, or adrenal cortex. It is also applied to monitor therapy in these settings. In the cosyntropin stimulation format, measurement at baseline and 60 minutes post-dose helps assess adrenal steroidogenic capacity and supports diagnosis and management of congenital adrenal hyperplasia and other causes of androgen excess. Androstenedione (also referred to as 4-androstenedione, delta-4-androstenedione, or 17-ketoestosterone) by itself does not localize the source of excess and should be interpreted alongside other hormone results.

Androstenedione is synthesized in Leydig cells of the testes, theca cells of the ovaries, and the adrenal zona reticularis. As a principal precursor to testosterone and estrone, it contributes to androgenic activity and figures prominently in virilizing disorders. Serum concentrations increase with ovarian sources of androgen excess, including polycystic ovary syndrome, hyperthecosis, and androgen-secreting tumors, and with adrenal sources such as Cushing syndrome and adrenal adenoma or carcinoma, as well as in congenital adrenal hyperplasia. Most circulating androstenedione is protein bound or conjugated; routine clinical assays report total androstenedione and do not differentiate free from bound fractions. Correlation with other endocrine tests is recommended because androstenedione values may not mirror the clinical severity of hyperandrogenism or identify the anatomic origin of excess androgen production.