Initial Workup for Hyperthyroidism Based on Philippine Clinical Practice Guidelines
The initial step in the workup of hyperthyroidism according to the Philippine Clinical Practice Guidelines is to measure thyroid-stimulating hormone (TSH) and free thyroxine (FT4) levels to confirm the diagnosis biochemically.
Diagnostic Approach
Initial Laboratory Evaluation
- Measure TSH and FT4 for case detection in symptomatic patients 1
- Low TSH with elevated FT4 confirms overt hyperthyroidism 1
- Low TSH with normal FT4 suggests subclinical hyperthyroidism 1
- Consider measuring T3 levels in highly symptomatic patients with minimal FT4 elevations, as this can help identify T3 toxicosis 1
Differential Diagnosis Workup
- If hyperthyroidism is confirmed biochemically, perform additional tests to determine the etiology 2:
- Consider TSH receptor antibody testing if there are clinical features and suspicion of Graves' disease (e.g., ophthalmopathy) 1
- Thyroid ultrasonography to evaluate for nodules or diffuse enlargement 2
- Thyroid scintigraphy (radioactive iodine uptake) to distinguish between causes of hyperthyroidism 2, 3
Special Considerations
- Low TSH with low FT4 is consistent with central hypothyroidism, which requires evaluation for hypophysitis 1
- Physical examination findings of ophthalmopathy or thyroid bruit are diagnostic of Graves' disease and should prompt early endocrine referral 1
- For patients with suspected thyroiditis, close monitoring is needed as the hyperthyroid phase is typically self-limited 1
Management Based on Severity
Asymptomatic or Mild Symptoms (Grade 1)
- Beta-blocker (e.g., atenolol or propranolol) for symptomatic relief 1
- Close monitoring of thyroid function every 2-3 weeks after diagnosis to detect transition to hypothyroidism 1
- For persistent thyrotoxicosis (>6 weeks), consider endocrine consultation for additional workup 1
Moderate Symptoms (Grade 2)
- Beta-blocker for symptomatic relief 1
- Hydration and supportive care 1
- Consider endocrine consultation 1
- For persistent thyrotoxicosis (>6 weeks), refer to endocrinology for additional workup and possible medical thyroid suppression 1
Severe Symptoms (Grade 3-4)
- Endocrine consultation for all patients 1
- Beta-blocker therapy 1
- Hydration and supportive care 1
- Consider hospitalization in severe cases 1
- Inpatient endocrine consultation can guide the use of additional medical therapies including steroids, SSKI, or thionamide (methimazole or propylthiouracil) 1
Follow-up Monitoring
- For subclinical hyperthyroidism (TSH 0.1-0.45 mIU/L), repeat testing within 3 months 1
- For more severe subclinical hyperthyroidism (TSH <0.1 mIU/L), repeat measurement along with FT4 and T3 within 4 weeks 1
- For patients with cardiac disease, atrial fibrillation, or other serious medical conditions, repeat testing within 2 weeks 1
- In cases of thyroiditis, monitor thyroid function regularly as it often progresses to hypothyroidism 1
Common Pitfalls to Avoid
- Failing to distinguish between different causes of hyperthyroidism, which require different treatment approaches 2, 3
- Missing the diagnosis of T3 toxicosis by not measuring T3 levels in symptomatic patients with normal FT4 4
- Overlooking thyroid dysfunction in pregnant women, which requires special consideration 5
- Not recognizing that thyroiditis is self-limited and the initial hyperthyroidism generally resolves in weeks with supportive care 1
Remember that proper diagnosis of the specific cause of hyperthyroidism is crucial for determining the appropriate treatment strategy and improving patient outcomes 2, 5.