Calculated free testosterone: rightful heir to the free thyroxine index?

Diagnosis of male hypogonadism relies on combining clinical features and total testosterone (T) measurement. Yet, androgen assessment stands at a familiar crossroads, reminiscent of the thyroxine (T₄) era, when total T₄ gave way to the free T₄ index and ultimately free T₄. Although calculated free T (cFT) is strongly linked to androgen-sensitive outcomes, a few critics contest its validity. Paradoxically, their vague recommendations to 'interpret total testosterone in relation to sex hormone-binding globulin (SHBG)' provide little practical guidance. They further advocate omitting cFT from the diagnostic workup of male hypogonadism, despite its ability to systematically correct for SHBG, thereby forfeiting a rational, evidence-based approach. We propose a pragmatic framework for diagnosing male hypogonadism and a research agenda to further validate cFT as a robust, clinically accessible tool.