Hyperthyroidism Lecture Notes

Introduction

• Topic: Hyperthyroidism
• Part of clinical medicine section
• Associated resources: notes, illustrations, quizzes, exam prep courses

Understanding Hyperthyroidism

• Definition: Condition where thyroid gland is overactive, producing excess T3 and T4 hormones.
• Types:
  • Primary Hyperthyroidism: Problem in the thyroid gland.
  • Secondary Hyperthyroidism: Problem in hypothalamus or pituitary gland.

Pathophysiology of Primary Hyperthyroidism

• Mechanisms:
  • Hyperfunctioning of thyroid follicles.
    • Causes high levels of T3 and T4.
    • TSH receptors are either hyperactive or overstimulated.
  • Destruction of thyroid follicles.
    • Releases thyroglobulin (TG), T3, and T4 into bloodstream.
• Causes:
  • Autoimmune stimulation (e.g., Graves' disease).
    • Overproduction of TSH receptor antibodies.
    • Presence of HLA mutations (DR3, B8).
  • Thyroid nodules producing excess hormones (e.g., toxic adenoma, multinodular goiter).
  • Exogenous intake of thyroid hormones (iatrogenic hyperthyroidism).

Secondary Hyperthyroidism

• Caused by pituitary adenomas producing excess TSH.
• Characteristics: Elevated TSH, T3, and T4 levels.

Common Findings in Hyperthyroidism

• Goiter: Enlargement of the thyroid gland.
• Metabolic Effects:
  • Weight loss
  • Heat intolerance
• Neurological Effects:
  • Agitation, anxiety, insomnia
  • Hyperactive deep tendon reflexes, tremors
• Cardiovascular Effects:
  • Tachycardia, high cardiac output
  • Systolic hypertension
• Gastrointestinal Effects:
  • Increased motility leading to diarrhea
• Reproductive Effects:
  • Menstrual irregularities, reduced libido, infertility

Specific Manifestations in Graves' Disease

• Exophthalmos (protruding eyes)
• Pretibial myxedema (swollen, hard skin on shins)

Complication: Thyroid Storm

• Extreme form of hyperthyroidism; life-threatening
• Triggered by stressors such as infections, surgery
• Symptoms: Hyperthermia, tachycardia, heart failure

Diagnosis

• Tests:
  • Measure TSH and T4 levels
  • Use imaging (e.g., pituitary MRI for secondary causes)
  • Radioactive iodine uptake scan for thyroid activity
  • Check for TSH receptor antibodies for Graves’ disease

Treatment

• General Management:
  • Use beta-blockers (e.g., propranolol) for symptomatic relief
  • Anti-thyroid medications (PTU, Methimazole) to reduce hormone synthesis
• Advanced Treatments:
  • Radioactive iodine ablation
  • Surgery (thyroidectomy)
• Managing Thyroid Storm:
  • Cooling measures
  • Beta-blockers for heart rate
  • PTU followed by iodine solution
  • Corticosteroids to inhibit T4 to T3 conversion

This summary captures the key points and essential concepts discussed in the lecture on hyperthyroidism, providing a comprehensive overview for review and study purposes.