Thyrotoxicosis: Causes, Symptoms, and Understanding Overactive Thyroid

Thyrotoxicosis is the clinical syndrome of excess thyroid hormone action, regardless of source. Hyperthyroidism (overproduction by the thyroid) is the most common cause.

Major Causes

• Graves' Disease: Autoimmune TSH-receptor antibodies stimulate thyroid overactivity (70-80% of cases).
• Toxic Nodular Goiter: Autonomous hyperfunctioning nodule(s).
• Toxic Multinodular Goiter: Multiple autonomous nodules.
• Subacute Thyroiditis: Viral inflammation causing transient hormone leak (painful thyroid).
• Amiodarone-Induced: Iodine-rich drug causing type 1 (iodine-induced synthesis) or type 2 (destructive thyroiditis).
• Struma Ovarii: Ovarian teratoma with thyroid tissue.
• Factitious Thyrotoxicosis: Surreptitious thyroid hormone ingestion.

Clinical Features

Symptoms mirror hyperthyroidism: weight loss, tachycardia, tremor, heat intolerance, anxiety, diarrhea, goiter (often), eye signs (Graves').

Diagnosis

Suppressed TSH, elevated free T4/T3. Etiology determined by uptake scan, antibodies, clinical context.

Treatment

Targeted to cause: antithyroid drugs, RAI, surgery, beta-blockers, corticosteroids (thyroiditis).