Maintaining euthyroidism: fundamentals of thyroid hormone physiology, iodine metabolism and hypothyroidism

Thyroid-related pathologies, especially subclinical and clinical hypothyroidism, are commonly described in clinical practice. While illnesses related to aberrant thyroid hormone homeostasis are the most prevalent endocrinological conditions diagnosed, important aspects related to thyroid hormone physiology are often overlooked. Further, the only known physiological purpose of iodine is its requirement for the synthesis of thyroxine (T4) and triiodothyronine (T3). However, although it can be applied as curative agent in the management of thyrotoxicosis, the halogen is often prescribed and used inappropriately with significant, but preventable clinical consequences. In an attempt to kindle a better understanding of aspects related to aberrant thyroid hormone regulation, iodine metabolism, and the clinical management of thyroid related pathology, the current paper provides a physiological and clinical overview of said constructs from a hypothyroid perspective.