Hormones

Editorial Perspective: As a physician, it is essential to comprehend normal physiology before one can grasp the concepts of pathophysiology. This is especially true for the thyroid gland and its disorders related to the skin. In this chapter, the synthesis, regulation, transport, metabolism, and actions of thyroid hormones are detailed. Understanding thyroid physiology will enable the clinician to utilize thyroid function tests appropriately. In addition, practitioners will gain an appreciation regarding why disorders that affect the dynamics of thyroid hormone have such profound and diverse clinical effects. The skin is a complex organ with vascular, neural, and muscular components. Aside from its role as protective barrier to infectious and non-infectious insults from outside world, it is a meta-bolically active organ that is vital in maintaining homeostasis. The skin is intimately involved in thermoregulation. Disorders that result in either hyperthyroidism or hypothyroidism will adversely affect how the skin performs its functions in maintaining homeostasis. Having knowledge of normal thyroid physiology will enable the clinician to recognize when abnormalities exist, allowing efforts to be made to return to the euthyroid state.