["Journal of Intellectual Disability Research, EarlyView. ", "\nABSTRACT\n\nBackground\nDown syndrome (DS) youth have an increased risk of metabolic syndrome (MetS). This study assessed the diagnostic performance of the triglyceride–glucose index (TyG) and its derivatives—TyG‐BMI, TyG‐waist circumference (WC) and TyG‐waist‐to‐height ratio (WHtR) in detecting MetS compared with traditional markers.\n\n\nMethods\nWe retrospectively analysed data from 60 DS patients and 40 controls; IR was estimated using HOMA‐IR, TyG, TyG‐BMI, TyG‐WC and TyG‐WHtR indices. MetS was defined by the presence of at least three of the following criteria: BMI z‐score ≥ 2 SD and/or WC/H ratio ≥ 0.5; fasting glucose > 100 mg/dL and/or pathological HOMA‐IR; dyslipidaemia; hypertension.\n\n\nResults\nMetS prevalence was 15% in DS. HOMA‐IR showed the highest sensitivity (0.667) and specificity (0.80) to detect MetS, while TyG demonstrated similar performance (sensitivity 0.667; specificity 0.843) and the best overall accuracy (0.817). Composite indices showed moderate accuracy but high specificity.\n\n\nConclusions\nTyG, being simple and cost‐effective, may be a valuable alternative for early MetS detection in DS.\n\n"]