Definition
Hyperthyroidism is a clinical syndrome caused by increased circulating levels of thyroid hormones (T3 and T4), leading to a hypermetabolic state. Graves’ disease is the most common cause; it’s an autoimmune disorder where IgG autoantibodies (TSHR-Ab) stimulate TSH receptors, mimicking TSH and causing excessive hormone production.
Etiology
- Primary cause: Graves' disease (autoimmune)
- Other causes:
- Toxic multinodular goiter
- Thyroid adenoma
- Thyroiditis (e.g., subacute)
- Iodine-induced hyperthyroidism (e.g., from contrast media or amiodarone)
- Graves' risk factors:
- Female sex
- Age 20–40
- Family history
- Thyroid storm: acute, life-threatening severe hyperthyroid state triggered by stress/infection/surgery.
Pathogenesis
- Thyroid hormone effects:
- ↑ Basal metabolic rate → ↑ oxygen consumption, calorigenesis
- ↑ Sensitivity to catecholamines → sympathomimetic effects (palpitations, tremor)
- In Graves' disease:
- Autoantibodies (TSHR-Ab) bind TSH receptor → continuous stimulation of hormone production
- Often associated with ophthalmopathy due to autoimmune infiltration in orbital tissue
- Occasionally accompanied by dermopathy (pretibial myxedema)
Symptoms
Hypermetabolic features:
- Weight loss (despite increased appetite) Heat intolerance, sweating
- Fatigue, restlessness
- Palpitations, tremor
- Muscle weakness
Neurologic/Psychiatric:
- Irritability, anxiety, insomnia
- Hyperkinesis, psychosis (severe cases)
Other findings:
- Menstrual irregularities
- Diarrhea or increased stool frequency
Graves’ disease classic triad:
- 1. Hyperthyroidism
- 2. Diffuse goiter
- 3. Exophthalmos (due to orbital fibroblast stimulation by cytokines)