Thyroid Disorders for PA
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Thyroid Disorders for the Physician Assistant Licensing Exam
Hyperthyroidism
- Pathophysiology
- Hyperthyroidism occurs due to excess production of thyroid hormones (T3 and T4), leading to increased metabolic activity.
- Common Causes:
- Graves’ Disease: Autoimmune activation of the TSH receptor, causing diffuse thyroid enlargement.
- Toxic Multinodular Goiter: Multiple overactive thyroid nodules.
- Toxic Adenoma: A single hyperfunctioning thyroid nodule.
- Thyroiditis: Inflammation leading to hormone release (e.g., subacute or silent thyroiditis).
- Iatrogenic: Excess thyroid hormone replacement or iodine exposure.
- Clinical Features
- Weight loss despite increased appetite, heat intolerance, sweating, palpitations, and tremor.
- Cardiovascular: Tachycardia, atrial fibrillation.
- Neurologic: Anxiety, tremors, hyperreflexia.
- Graves' Disease: Exophthalmos and pretibial myxedema.
- Diagnosis
- Low TSH and elevated free T4/T3.
- RAIU Scan: Diffuse uptake in Graves' disease; focal in toxic adenoma.
- Management
- Antithyroid Drugs: Methimazole (first-line) or PTU (pregnancy).
- Beta-blockers: Propranolol to manage symptoms.
- Radioactive Iodine or Surgery for definitive treatment.
Hypothyroidism
- Pathophysiology
- Hypothyroidism results from inadequate thyroid hormone production.
- Common Causes:
- Hashimoto’s Thyroiditis: Autoimmune destruction of the thyroid gland.
- Iatrogenic: Post-thyroidectomy or radioactive iodine therapy.
- Medications: Lithium, amiodarone.
- Clinical Features
- Fatigue, weight gain, cold intolerance, constipation, dry skin, and bradycardia.
- Neurologic: Depression, cognitive slowing.
- Severe Cases: Myxedema coma presents with hypothermia and altered mental status.
- Diagnosis
- High TSH and low free T4 (primary hypothyroidism).
- Low TSH and low T4 (central hypothyroidism).
- Anti-TPO antibodies elevated in Hashimoto’s.
- Management
- Levothyroxine (T4): Synthetic hormone replacement. Dosing is based on TSH levels.
- Myxedema Coma: Requires high-dose IV levothyroxine and supportive care.
Key Points
- Hyperthyroidism: Commonly caused by Graves’ disease, toxic multinodular goiter, or toxic adenoma. Diagnosed by low TSH and elevated free T4/T3. Managed with antithyroid medications, beta-blockers, or definitive treatments like radioactive iodine or surgery.
- Hypothyroidism: Most often caused by Hashimoto’s thyroiditis. Diagnosed by high TSH and low free T4. Treated with levothyroxine.
- Complications: Thyroid storm in hyperthyroidism and myxedema coma in hypothyroidism are life-threatening and require emergency care.