Steroid hormones such as testosterone or vitamin D are vital for human physiology. In circulation, steroid hormones bind to albumin and specific binding proteins (BP) with only a small fraction circulating freely. The free hormone hypothesis suggests that this free fraction best reflects the biological activity. Though experimental and clinical data support this, routinely available methods measure total steroid hormone levels. Relying on total hormone levels could lead to misrepresentation of the hormonal status, especially in conditions where BP production is altered (organ failure, obesity, pregnancy), impairing correct diagnosis and treatment. Direct free hormone measurements are only performed in specialized research labs and not available in clinical routine. Formulas to estimate free steroid hormone concentrations have been developed, but their applicability in many clinical conditions is questionable, so is the correctness of therapeutic actions based on these results. With BEED-ED, we will improve the clinical applicability of free steroid hormone concentrations in patients with specific conditions by using state-of-the-art methodology. Specifically, we will establish reference ranges in healthy subjects and investigate the reliability of free hormone estimates in individuals with alterations in BP production and/or binding affinity. Based on these findings, we will improve current formulas and, if needed, develop condition-specific calculators to better estimate free hormone levels. We will evaluate the impact of frequently used BP assays on calculated free steroid hormone results and survey the use of free hormone calculators and access to direct measurements in Flanders and Europe. Ultimately, the project will result in the development of clinical sample workflows based on screening of free steroid hormone levels by calculation and if needed sample referral to reference laboratories for direct measurements.