What happens during hyperthyroidism?

Hyperthyroidism: Clinical Manifestations and Systemic Effects

Hyperthyroidism is characterized by excessive thyroid hormone production leading to multiple systemic manifestations including tremors, nervousness, insomnia, excessive sweating, heat intolerance, tachycardia, hypertension, and goiter. 1, 2

Clinical Manifestations

• Cardiovascular symptoms: Tachycardia, hypertension, and potential heart failure in severe cases 2, 1
• Neuropsychiatric symptoms: Nervousness, hyperactivity, insomnia, and anxiety 1, 3
• Dermatologic manifestations: Excessive sweating, heat intolerance, hair loss 2, 1
• Ophthalmologic signs: Eyelid lag or retraction, particularly in Graves' disease 2
• Gastrointestinal effects: Weight loss, diarrhea 3
• Physical findings: Goiter (enlarged thyroid gland), pretibial myxedema in Graves' disease 2

Diagnostic Findings

• Biochemically characterized by suppressed thyroid-stimulating hormone (TSH) with elevated free thyroxine (FT4) and/or triiodothyronine (T3) levels 2, 3
• Graves' disease, the most common cause (95% of hyperthyroidism cases in pregnancy), presents with distinctive ophthalmic signs and dermal manifestations 2, 3
• Other causes include toxic multinodular goiter, toxic adenoma, and thyroiditis 4, 3

Systemic Complications

• Cardiovascular complications: Decreased systemic vascular resistance, increased cardiac output, potential pulmonary hypertension, and atrial fibrillation 1, 4
• Bone health: Untreated hyperthyroidism can lead to osteoporosis 3
• Pregnancy complications: Increased risk for severe preeclampsia, preterm delivery, heart failure, miscarriage, and low birth weight in neonates 2, 1
• Thyroid storm: A rare but life-threatening emergency characterized by severe acute exacerbation of hyperthyroidism symptoms requiring immediate medical intervention 2, 4

Treatment Approaches

• Pharmacological management:

  • Beta-blockers (atenolol, propranolol) to control heart rate and reduce tremors 1
  • Antithyroid medications (methimazole, propylthiouracil) to reduce thyroid hormone production 5, 6, 7
  • Careful monitoring required with antithyroid medications due to potential side effects including agranulocytosis and liver damage 6, 7

• Definitive treatment options:

  • Radioactive iodine ablation (most widely used in the United States) 5, 3
  • Surgical thyroidectomy 5, 4

Special Considerations

• Pregnancy: Requires careful monitoring and treatment adjustment; propylthiouracil may be preferred in first trimester, with potential switch to methimazole for second and third trimesters due to propylthiouracil's hepatotoxicity risk 6, 7
• Pediatric patients: Methimazole is generally preferred over propylthiouracil due to lower risk of severe liver injury 7, 8
• Drug interactions: Hyperthyroidism affects metabolism of several medications including anticoagulants, beta-blockers, digitalis glycosides, and theophylline; dosage adjustments may be needed when transitioning from hyperthyroid to euthyroid state 6, 7

Monitoring and Follow-up

• Regular thyroid function tests to guide therapy 6, 7
• Monitoring for treatment complications including hepatic dysfunction, agranulocytosis, and vasculitis 6, 7
• Long-term follow-up needed as definitive treatments often lead to hypothyroidism requiring lifelong thyroid hormone replacement 3