Non-visualization of the inferior thyroid arteries on B-mode ultrasound is associated with structural inferior thyroid artery abnormalities and an adverse vascular phenotype

Background Non-visualization of one or both inferior thyroid arteries (ITAs) on B-mode ultrasound is regarded as an anatomical variant, but its clinical significance remains unclear. We investigated whether ITA non-visualization reflects structural arterial abnormality and whether it is associated with carotid ultrasound markers of vascular phenotype and an adverse cardiometabolic profile. Methods ITA assessment was validated against computed tomography (CT) in 47 clinically referred participants who had undergone both examinations. Reproducibility was assessed in 201 participants from the IMPROVE cohort. Cross-sectional associations with cardiovascular risk factors, carotid ultrasound phenotypes, and cardiovascular risk scores were examined in 2843 participants from the same cohort without thyroid disease, classified according to the number of non-visible ITAs (0, 1, or 2). Final ITA classification was based on artificial intelligence-assisted, human-validated review. Results ITA non-visualization frequently corresponded to arterial absence, marked caliber reduction, or aberrant anatomy. After anatomical adjudication, ultrasound–CT agreement was excellent (overall concordance 0.95; Cohen's kappa 0.84). Scan–rescan reproducibility was excellent. Increasing numbers of non-visible ITAs were associated with older age (β = 0.08, P = 0.0014), higher mean carotid intima–media thickness (β = 0.046, P = 0.044), greater vascular risk-factor burden (β = 0.09, P = 0.0004), a less favorable cardiometabolic profile, and higher cardiovascular risk scores across algorithms (all P-trend <0.01). Conclusions ITA non-visualization is unlikely to represent only an anatomical variant. It frequently reflects structural ITA abnormalities and is associated with higher mean carotid intima–media thickness and a more adverse cardiometabolic profile. These findings support evaluation of ITA non-visualization as an adjunctive descriptor of an adverse vascular phenotype.