When to order Thyroid-Stimulating Hormone (TSH) test?

When to Order TSH Testing

TSH testing should be ordered for patients with symptoms suggestive of thyroid dysfunction, those with high-risk factors for thyroid disease, and in specific clinical scenarios requiring thyroid monitoring, but routine population screening is not recommended for asymptomatic individuals without risk factors. 1

Indications for TSH Testing

Symptomatic Patients

Order TSH for patients presenting with:

• Hypothyroidism symptoms: fatigue, weight gain, cold intolerance, constipation, dry skin, depression, menstrual irregularities 1, 2
• Hyperthyroidism symptoms: weight loss, palpitations, heat intolerance, tremor, anxiety 1
• Unexplained clinical findings: atrial fibrillation, unexplained dyslipidemia, cognitive decline, or unexplained glycemic variations in diabetic patients 1

High-Risk Populations

TSH testing is warranted in:

• Elderly patients (especially women >60 years) 1, 3
• Postpartum women 1
• Patients with autoimmune disorders (especially Type 1 diabetes) 1
• Patients with radiation exposure (>20 mGy to thyroid area) 1
• Patients with Down syndrome 1
• Individuals with family history of thyroid disease 1
• Patients with personal history of thyroid disease or surgery 1
• Women planning pregnancy or in first trimester 4

Monitoring Scenarios

TSH testing is indicated for:

• Patients on thyroid hormone replacement therapy:

  • 6-8 weeks after any dosage change 4
  • Every 6-12 months for stable adult patients 4
  • More frequently in pediatric patients or when clinical status changes 4

• Patients on immune checkpoint inhibitors: Monitor for hypophysitis which can affect thyroid function 1

• Patients with Type 1 diabetes:

  • At diagnosis when clinically stable
  • Every 1-2 years thereafter
  • Sooner if symptoms of thyroid dysfunction develop 1

• Pregnant women with pre-existing hypothyroidism:

  • As soon as pregnancy is confirmed
  • At minimum during each trimester 4

When NOT to Order TSH

• Routine screening of asymptomatic general population is not recommended 1
• Hospitalized patients with acute illness (may have falsely abnormal results due to non-thyroidal illness) 1

Interpretation and Follow-up

• If TSH is abnormal, follow up with free T4 testing on the same sample 1
• For low TSH with normal T4 (subclinical hyperthyroidism) or high TSH with normal T4 (subclinical hypothyroidism), consider:
  • Repeat testing in 3-6 months to confirm persistence 1
  • Additional thyroid antibody testing (TPO, TG) to assess risk of progression 1

Clinical Pitfalls to Avoid

• Don't rely solely on clinical examination to rule out thyroid dysfunction, as symptoms can be subtle or overlap with other conditions 5
• Don't dismiss mild TSH abnormalities in elderly patients, as subclinical thyroid disease is common and may have significant health impacts 3, 5
• Don't interpret TSH in isolation during acute illness, as non-thyroidal illness can affect results 1
• Don't forget to check TSH when evaluating unexplained changes in glycemic control in diabetic patients 1
• Don't miss thyroid dysfunction in patients with depression or cognitive changes, especially in elderly patients 3

By following these evidence-based guidelines for TSH testing, clinicians can appropriately identify patients who would benefit from thyroid function assessment while avoiding unnecessary testing in low-risk, asymptomatic individuals.