The Thyroid–Metabolism Axis: Pathways of Dysregulation and the Effects of Treatment

Thyroid hormones regulate a complex and interconnected network of metabolic signaling. Thyroid dysfunction is, at present, defined and monitored through circulating thyroid-stimulating hormone (TSH) and free thyroid hormones. However, biochemical normalization does not entirely indicate restoration of metabolic homeostasis. This discrepancy highlights a critical limitation of the current TSH-centric paradigm, which also fails to explain the heterogeneity in cardiometabolic outcomes observed among patients with similar biochemical profiles. Metabolomics, through the analysis of tissue-specific biofluids, could aid in capturing the complex metabolic perturbations that characterize this disease. In this review, we summarize metabolomic signatures typical of thyroid dysfunction, perform a critical evaluation of limitations and variability across studies, and explore the clinical and translational implications of metabolomics in thyroid pathology. In addition, five metabolic hubs influenced by thyroid hormone activity are summarized: (i) lipid and lipoprotein remodeling; (ii) mitochondrial energetics and redox balance; (iii) amino acid metabolism and protein turnover; (iv) gut–liver–thyroid axis and (v) biological impact of subclinical thyroid diseases. Taken together, these findings challenge the sufficiency of a diagnostic model based on TSH measurement and pose metabolomics as a promising tool to refine risk stratification, uncover subclinical vulnerability and guide patient-centered management of thyroid disease. Despite its promise, clinical adoption of metabolomics is hindered by a lack of standardization and complex data interpretation. To overcome these limitations, coupling metabolomics with genomics and transcriptomics may allow its translation into practical application.