Thyrotoxicosis

**Definition:** Thyrotoxicosis is defined as an elevated level of free thyroid hormone in serum (from any source) and suppression of thyroid-stimulating hormone (TSH). If it is caused by overproduction and secretion from the thyroid gland, it is called hyperthyroidism.

**Long definition:** Thyrotoxicosis is the hypermetabolic condition associated with elevated levels of free thyroxine (FT4) and/or free triiodothyronine (FT3). Hyperthyroidism includes diseases that are a subset of thyrotoxicosis, that are caused by excess synthesis and secretion of thyroid hormone by the thyroid; they are not associated with exogenous thyroid hormone intake and subacute thyroiditis. Most clinicians, exclusive of endocrinologists, use the terms hyperthyroidism and thyrotoxicosis interchangeably. The causes of thyrotoxicosis include Graves disease, an organ-specific autoimmune disorder characterized by a variety of circulating antibodies, subacute thyroiditis (approximately 15-20%), a destructive release of preformed thyroid hormone, toxic multinodular goiter (Plummer disease), toxic adenoma (a single hyperfunctioning follicular thyroid adenoma).. Symptoms present as weight loss despite enhanced appetite, heat intolerance, palpitations, tremor, and hyperdefecation.

**Exclusions:** - Transitory neonatal hyperthyroidism