What is the appropriate diagnostic workup and treatment for a 17-year-old male presenting with unintentional weight loss, palpitations, and heat?

Diagnostic Workup for Unintentional Weight Loss, Palpitations, and Heat Intolerance in a 17-Year-Old Male

The constellation of unintentional weight loss, palpitations, and heat intolerance in a 17-year-old male strongly suggests hyperthyroidism and requires prompt thyroid function testing as the initial diagnostic step. 1

Initial Diagnostic Workup

• Obtain thyroid function tests including TSH, free T4, and free T3 as the first-line laboratory investigation, as these symptoms strongly suggest thyroid dysfunction 1
• Perform a 12-lead ECG to assess for tachycardia, arrhythmias, or other cardiac abnormalities that may be related to thyroid dysfunction or other causes 2
• Check vital signs with particular attention to heart rate, blood pressure, and temperature to evaluate for tachycardia and hypertension 3
• Physical examination should focus on:
  • Thyroid gland assessment (size, tenderness, nodules) 3
  • Cardiac examination for tachycardia, irregular rhythm, or murmurs 3
  • Skin assessment for moisture, texture, and temperature 3
  • Eye examination for proptosis or lid lag (signs of Graves' disease) 3
  • Tremor assessment and reflexes 3

Secondary Diagnostic Testing

• If initial thyroid function tests suggest hyperthyroidism (suppressed TSH with elevated T4/T3), additional testing should include:
  • Thyroid antibodies (TSI, TRAb, TPO) to determine if Graves' disease is the underlying cause 3
  • Thyroid ultrasound to evaluate for nodules, increased vascularity, or other structural abnormalities 3
• If initial thyroid testing is normal, proceed with:
  • Complete blood count to assess for infection, anemia, or malignancy 4
  • Basic metabolic panel to evaluate electrolyte abnormalities and kidney function 4
  • Liver function tests to screen for hepatic disorders 4
  • C-reactive protein and erythrocyte sedimentation rate to assess for inflammatory conditions 4
  • Fasting glucose and HbA1c to evaluate for diabetes 4
  • Urinalysis to screen for renal disease or infection 4

Cardiac Evaluation

• For persistent palpitations, a 48-hour ambulatory ECG monitoring is recommended to identify potential arrhythmias 2
• If palpitations are frequent or sustained, consider echocardiography to exclude structural heart disease 2
• For less frequent episodes, an event recorder or implantable loop recorder may be considered if symptoms persist without diagnosis 2

Additional Testing Based on Initial Results

• If initial workup is unrevealing, consider:
  • Chest radiography to screen for pulmonary or mediastinal pathology 4
  • Abdominal imaging if gastrointestinal symptoms are present 5
  • Screening for substance use (stimulants, drugs) that could cause similar symptoms 3
  • Evaluation for pheochromocytoma with 24-hour urinary fractionated metanephrines or plasma metanephrines if hypertension is present 3

Management Considerations

• If hyperthyroidism is confirmed:

  • Initiate treatment with methimazole as first-line therapy 1
  • Monitor for potential side effects of treatment including rash, joint pain, and agranulocytosis 6
  • Avoid sympathomimetic agents which may worsen cardiac symptoms 6
  • Consider beta-blockers for symptom control (palpitations, tachycardia) while awaiting definitive treatment 6

• If cardiac arrhythmias are detected:

  • Management should follow guidelines for the specific arrhythmia identified 3
  • For supraventricular tachycardia, consider vagal maneuvers, beta-blockers, or referral for electrophysiology evaluation 3

Indications for Specialist Referral

• Refer to endocrinology if hyperthyroidism is confirmed for specialized management 3
• Refer to cardiology/electrophysiology if:
  • Complex arrhythmias are detected 2
  • Palpitations are associated with syncope or pre-syncope 2
  • Structural heart disease is identified 2

Common Pitfalls to Avoid

• Do not attribute symptoms solely to anxiety without excluding organic causes, particularly thyroid dysfunction 1
• Do not delay thyroid function testing when this symptom triad is present 1
• When treating hyperthyroidism, always screen for adrenal insufficiency before initiating therapy, as thyroid hormone increases metabolic clearance of glucocorticoids 6
• In patients with both adrenal insufficiency and hypothyroidism, always start steroids before thyroid hormone to prevent adrenal crisis 6