thyrotoxicose

Thyrotoxicosis is a clinical state produced by excess circulating thyroid hormones, typically triiodothyronine (T3) and thyroxine (T4), regardless of the source. It results from increased production or release of hormones, or from exogenous intake. The most common causes are Graves disease, toxic multinodular goiter, and thyroiditis; other causes include excess iodine exposure and thyroid hormone medications. Thyrotoxicosis describes the hormonal excess, while the underlying conditions that cause it are hyperthyroidism in many cases.

Clinical features include a hypermetabolic state with weight loss and preserved appetite, heat intolerance, sweating, tremor, anxiety, palpitations, tachycardia, and sometimes hypertension or insomnia. Fatigue and proximal muscle weakness are common. Women may experience menstrual changes. In older adults, presentations can be subtle or dominated by atrial fibrillation or heart failure. Eye signs and pretibial myxedema are characteristic of Graves disease.

Diagnosis rests on laboratory and sometimes imaging findings. Serum TSH is typically suppressed, with elevated free T4 and/or free T3. If discordant, free T3 measurement may help. Autoantibodies, such as TSH receptor antibodies, support Graves disease; thyroid peroxidase antibodies may be present. Imaging with a radioactive iodine uptake scan helps distinguish etiologies: high uptake suggests Graves or nodular disease, while low uptake points to thyroiditis or exogenous hormone use.

Treatment depends on the cause and severity. Beta-blockers provide symptomatic relief. Antithyroid drugs such as methimazole are commonly used; propylthiouracil is preferred in pregnancy or certain contexts. Radioactive iodine therapy or thyroidectomy are options for definitive treatment. In thyroid storm, urgent management includes thionamides, inorganic iodide after thionamides, glucocorticoids, aggressive cooling and fluids, and treatment of precipitating factors. Prognosis is generally favorable with appropriate management, though risks include atrial fibrillation, heart failure, osteoporosis, and eye disease in Graves.