- Last edited on January 29, 2021
Hyperthyroidism
Primer
Hyperthyroidism is an autoimmune disorder of the endocrine system where the thyroid gland produces excess thyroid hormone. Hyperthyroidism can accelerate the body's metabolism, and can cause unintentional weight loss and systemic symptoms and changes.
Epidemiology
- The prevalence of hyperthyroidism is around 1%.[1]
Etiologies
Graves Disease
Graves Disease is the most common cause of hyperthyroidism. Grave's Disease occurs when thyroid stimulating immunoglobulin binds to the thyroid-stimulating hormone (TSH) receptor in the thyroid, and stimulates the action of the thyroid-stimulating hormone. Triggers for Grave's includes pregnancy (tyically postpartum), excess iodine intake, infections, emotional stressors, smoking, and other infectious stressors.
Toxic Multinodular Goiter
Toxic Multinodular Goiter are nodules (typically benign) that develop in the thyroid gland and produce thyroid hormone without the corresponding response to homeostatic signals to maintain a euthyroid state.
Other
Other causes of hyperthyroidism include thyroid storm and Jod-Basedow phenomenon.
Comparison
Hypothyroidism vs. Hyperthyroidism
| Hypothyroidism | Hyperthyroidism | |
|---|---|---|
| Neuropsychiatric | Hypo-activity, lethargy, fatigue, weakness, depressed mood, reflexes (delayed, diminished) | Hyperactivity, restlessness, anxiety, insomnia, fine tremors (due to increased β-adrenergic activity), reflexes (brisk) |
| Ocular | Periorbital edema | Ophthalmopathy in Graves disease (including periorbital edema, exophthalmos), lid lag/retraction |
| Metabolic | Cold intolerance, decreased sweating, weight gain (due to lowered basal metabolic rate), hyponatremia (due to decreased free water clearance) | Heat intolerance, sweating, weight loss |
| Cardiovascular | Bradycardia, dyspnea on exertion (cardiac output) | Tachycardia, palpitations, dyspnea, arrhythmias (e.g. - atrial fibrillation), chest pain, hypertension |
| Gastrointestinal | Constipation. decreased appetite | Diarrhea, increased appetite |
| Dermatologic | Dry cool skin, coarse brittle hair, diffuse alopecia, brittle nails; puffy facies and generalized nonpitting edema (myxedema) | Warm moist skin, fine hair, onycholysis, pretibial myxedema in Graves disease |
| Reproductive | Abnormal uterine bleeding, decreased libido, infertility | Abnormal uterine bleeding, gynecomastia, decreased libido, infertility |
| Laboratory Findings | • Elevated TSH • Decreased free T3 and T4 • Hypercholesterolemia (due to decreased LDL receptor expression) | • Decreased TSH • Elevated free T3 and T4 • Decreased LDL, HDL, and total cholesterol |