Central sensitivity to thyroid hormone indices and glucose metabolism disorders

The central sensitivity to thyroid hormone shows the negative feedback capacity of free thyroxine levels to the pituitary gland. Clinical studies have continuously demonstrated the correlation between the central sensitivity to thyroid hormone and impaired glucose metabolic homeostasis，and positive or negative relationship were found. Different indices selected to assess central thyroid hormone sensitivity, different risk events concerned, and ethnic reasons may be responsible for the conflicting results between studies. This narrative review combined with the latest research progress to demonstrate the association between the indices commonly used for assessing the degree of central sensitivity to thyroid hormone and the prevalence of type 2 diabetes mellitus, prediabetes, gestational diabetes mellitus, obesity, metabolic syndrome, and other glucose metabolism-related diseases in clinical research. This review includes not only the classical thyrotroph T4 resistance index and thyroid-stimulating hormone index but also the thyroid feedback quantile-based index and parametric thyroid feedback quantile-based index, which have recently attracted much attention. By summarizing and reviewing the literature, we attempt to explain the interaction between the thyroid hormone and the glucose metabolic system from a new perspective, thereby helping us to further explore the complex association between these two significant endocrine regulatory networks.