Nathalie Reix, François Fraissinet, Safouane Hamdi, Jean Guibourdenche, David Guénet, Manuela Lotierzo, Valérie Moal, Véronique Raverot, Julie Brossaud, Groupe de Biologie Hormonale et Spécialisée
This article, presenting three clinical cases, discusses the analytical issues of testosterone measurement in blood (immunoassay and liquid chromatography and mass spectrometry). It also describes the different circulating testosterone fractions (total, free and bioavailable) and how to measure or calculate them. Beyond these analytical aspects, the article addresses the challenges encountered in establishing reference ranges and the specific difficulties related to different patient populations: men, women and children. Finally, in light of the evidence outlined in the article, we review the three cases.