Overview
Why Excess Thyroid Hormone Becomes Dangerous
Graves disease is an autoimmune cause of hyperthyroidism.
Graves disease is an autoimmune cause of hyperthyroidism. Thyroid-stimulating immunoglobulins bind to the thyroid-stimulating hormone receptor and keep the gland switched on. The thyroid releases excessive T4 and T3 even though the pituitary has already suppressed TSH. Thyroid hormone increases metabolic activity and amplifies the body’s response to catecholamines. The patient may have weight loss despite increased appetite, heat intolerance, sweating, fine tremor, anxiety, diarrhea, tachycardia, and insomnia. Older adults may show a less dramatic picture: new atrial dysrhythmias, unexplained weight loss, weakness, or worsening heart failure can be the clue. A diffusely enlarged thyroid and Graves ophthalmopathy support Graves disease, but neither finding confirms it alone. Hyperthyroidism from thyroiditis, a toxic nodule, or excessive thyroid hormone replacement can produce many of the same symptoms. The cause matters because thionamides work only when the thyroid is actively synthesizing hormone.