What are the symptoms of hyperthyroidism and what blood work is needed to confirm diagnosis?

Symptoms of Hyperthyroidism and Diagnostic Blood Work

The diagnosis of hyperthyroidism requires measuring TSH, Free T4, and Free T3 (or Total T3) levels, with a low TSH and elevated thyroid hormones confirming the diagnosis. 1, 2, 3

Clinical Presentation of Hyperthyroidism

Common symptoms and signs of hyperthyroidism include:

• Cardiovascular symptoms:

  • Palpitations
  • Tachycardia
  • Atrial fibrillation (especially in elderly)

• Metabolic symptoms:

  • Unintentional weight loss
  • Heat intolerance
  • Increased appetite
  • Fatigue

• Neuropsychiatric symptoms:

  • Anxiety
  • Insomnia
  • Restlessness
  • Tremors

• Gastrointestinal symptoms:

  • Diarrhea
  • Increased bowel movements

• Other symptoms:

  • Sweating
  • Muscle weakness
  • Menstrual irregularities in women

• Physical examination findings:

  • Diffusely enlarged thyroid gland (in Graves' disease)
  • Exophthalmos or lid retraction (in Graves' disease)
  • Warm, moist skin
  • Fine tremor
  • Hyperreflexia 3

Diagnostic Blood Work

Initial Testing

1. TSH (Thyroid Stimulating Hormone):

   • First-line test with high sensitivity (98%) and specificity (92%)
   • Low or suppressed TSH (<0.1 mIU/L) suggests hyperthyroidism 4, 1

2. Free T4 (Thyroxine):

   • Elevated in overt hyperthyroidism
   • May be normal in T3-toxicosis 1, 2

3. Free T3 or Total T3 (Triiodothyronine):

   • Important to measure as some patients have isolated T3 elevation
   • Critical for detecting T3-toxicosis where only T3 is elevated 1, 3

Follow-up Testing

If initial tests confirm hyperthyroidism, additional tests to determine etiology:

1. TSH-Receptor Antibodies:

   • Positive in Graves' disease
   • Helps differentiate from other causes of hyperthyroidism 1, 2, 3

2. Thyroid Peroxidase (TPO) Antibodies:

   • Often positive in autoimmune thyroid disorders
   • Can help confirm Graves' disease diagnosis 5

3. Thyroid Ultrasound:

   • Evaluates thyroid size and structure
   • Identifies nodules or diffuse enlargement 1, 5

4. Radioactive Iodine Uptake and Scan:

   • Differentiates between destructive thyroiditis and hyperthyroidism due to Graves' disease or toxic nodular goiter
   • Increased uptake in Graves' disease and toxic nodules
   • Decreased uptake in thyroiditis 1, 2, 3

Interpretation of Results

• Overt Hyperthyroidism:

  • Low/suppressed TSH + elevated Free T4 and/or Free T3

• Subclinical Hyperthyroidism:

  • Low/suppressed TSH + normal Free T4 and Free T3 3

• T3-Toxicosis:

  • Low TSH + normal Free T4 + elevated Free T3 1, 6

Important Considerations

• Repeat TSH testing within 2-4 weeks to confirm initial findings, with more urgent repeat testing (within 2 weeks) for patients with atrial fibrillation, cardiac disease, or other serious medical conditions 1

• Be aware that certain medications (glucocorticoids, dopamine, amiodarone) and non-thyroidal illnesses can affect thyroid function test results 1, 3

• Untreated hyperthyroidism can lead to serious complications including cardiac arrhythmias, heart failure, osteoporosis, and increased mortality 2, 3

• Thyroid storm is the most severe form of thyrotoxicosis, characterized by altered mental status, and requires immediate treatment 7

• In elderly patients, a low TSH is not always associated with hyperthyroidism and requires careful evaluation 6

By systematically evaluating symptoms and obtaining appropriate laboratory tests, hyperthyroidism can be accurately diagnosed and properly managed to prevent complications and improve outcomes.