The Short Version
Low testosterone is a well-documented contributor to reduced libido, but no authoritative clinical source identifies it as the "primary" cause. Major medical references — including the Merck Manual, Mayo Clinic, Cleveland Clinic, and the Endocrine Society — consistently describe male libido as multifactorial, with psychological factors (depression, anxiety, relationship problems), medications, chronic conditions, and lifestyle factors frequently playing equal or greater roles. The claim conflates testosterone's important role with singular primacy, an assertion the clinical evidence does not support.