Emergencies in Thyroid Function

Abstract

The thyroid gland can be an overlooked source of a medical emergency. This butterfly-shaped gland is located just inferior to the larynx on the anterior neck and is responsible for the metabolic rate of many processes in the human body. A hyperthyroid state elevates the rate of metabolism, and a hypothyroid state is cause for a decreased metabolic rate. Thyroid hormone is released based on a negative feedback mechanism. As the level of thyroid hormone falls, the hypothalamus is stimulated to secrete thyroid-releasing hormone, which in turn stimulates the pituitary gland to release thyroid-stimulating hormone (TSH), which in turn acts on the thyroid gland to release thyroxine (T4). Thyroid function is based on the level of TSH. In ah ypothyroid state, the TSH is elevated, and in a hyperthyroid state, the TSH is reduced (Table 1). The actual effects of the thyroid hormone can take days bto weeks to manifest. Certain extrinsic factors can increase the release of thyroid hormone (Table 2). These factors can include exposure to cold and various emotional reactions. Thyroid hormone is responsible for 2 very basic needs in the body. First, it is responsible for growth and development in children as well as mental development and attainment of sexual maturity. Second, it is responsible for the metabolism of nearly all body tissues with the exception of the retina, spleen, testes, and lungs. The basal metabolicratecanincrease60%to70%abovenormalwhenlarge amounts of thyroid hormone are present. 1 Thyroid hormone increases heart rate, contractility, and vasodilation. Gastrointestinal secretions are increased, along with motility and appetite. The sympathetic nervous system is stimulated, producing tachycardia, palpitations, sweating, and tremor. Drugs that block sympathetic response (eg, β-blockers) have proved useful in addressing the manifestations of excess thyroid hormone.