Testosterone

Testosterone is the primary anabolic androgen, produced mainly by Leydig cells in males and the adrenal cortex and ovaries in females, driving muscle protein synthesis, erythropoiesis, bone density, and competitive drive. Salivary testosterone represents the free, bioavailable fraction (approximately 1–3% of total) as it passively diffuses through salivary gland acinar cells, making it a highly sensitive index of bioavailable androgen status. Hackney et al. (2008) and Groeneveld et al. (2009) validated salivary testosterone as a reliable non-invasive alternative to serum for monitoring endocrine responses to training load.