In PCOS laboratory assessment, which parameter most directly reflects circulating free androgen activity?

• A. Free testosterone
• B. SHBG
• C. FSH
• D. LH

Answer: (A)

The biologically active portion of circulating androgens is the free fraction, so the parameter that best reflects circulating free androgen activity is free testosterone. Because much of testosterone is bound to SHBG, total testosterone can be misleading when SHBG levels vary (as they often do in PCOS due to insulin resistance). Free testosterone accounts for both the amount of testosterone and how much is available to act on tissues, making it a more direct measure of androgen action. In PCOS, lower SHBG can raise the free fraction even if total testosterone isn’t markedly high, reinforcing why free testosterone tracks androgen activity more closely. Measuring it directly or via a calculated value using total testosterone, SHBG, and albumin provides the most accurate reflection of circulating androgen activity. SHBG modifies availability but doesn’t quantify activity itself, and FSH/LH relate to ovarian regulation rather than direct androgen action.