thyrotoxic

Thyrotoxic is an adjective relating to thyrotoxicosis, the clinical state caused by excess thyroid hormone. In medical use, thyrotoxicosis denotes elevated circulating T3 and T4 with a suppressed TSH, regardless of the underlying cause.

Causes include autoimmune hyperthyroidism such as Graves disease, toxic multinodular goiter or toxic adenomas, thyroiditis with a thyrotoxic phase, and exogenous thyroid hormone excess. Iodine-induced thyrotoxicosis and medication-associated thyroid toxicity (for example from amiodarone) are additional possibilities. Severe thyrotoxic states can progress to thyroid storm, a life-threatening emergency.

Pathophysiology involves excess thyroid hormone acting on cellular receptors to increase metabolic rate and adrenergic activity. Clinically, patients may present with weight loss, heat intolerance, sweating, tachycardia or arrhythmias, tremor, anxiety, fatigue, and a goiter. Ophthalmopathy may accompany Graves disease.

Diagnosis combines clinical assessment with laboratory data: suppressed TSH with elevated free T4 and/or free T3. Autoimmune markers such as thyroid-stimulating immunoglobulins help identify Graves disease; a radioactive iodine uptake scan can help distinguish etiologies.

Management targets the underlying cause and symptom control. Beta-blockers relieve adrenergic symptoms. Antithyroid drugs (methimazole or propylthiouracil) reduce hormone synthesis. Definitive therapy includes radioactive iodine ablation or thyroidectomy. In iodine-induced or thyroiditis-related thyrotoxicosis, treatment varies; thyroid storm requires intensive care with cooling, fluids, antithyroid drugs, iodide after antithyroid therapy, beta-blockade, and glucocorticoids.

Note: while the term thyrotoxic is used, many guidelines prefer thyrotoxicosis. Prognosis depends on the cause and response to treatment.