When should elevated Thyroid-Stimulating Hormone (TSH) levels be treated in adults, including older adults and pregnant women?

When to Treat Elevated TSH

Treat elevated TSH immediately with levothyroxine when TSH is persistently >10 mIU/L regardless of symptoms, or at any TSH elevation if the patient is symptomatic, pregnant, or planning pregnancy. 1, 2

Confirm the Diagnosis First

Before initiating treatment, always confirm elevated TSH with repeat testing after 2-3 months, as 30-60% of elevated TSH levels normalize spontaneously. 1, 2, 3, 4 This critical step prevents unnecessary lifelong treatment for transient thyroid dysfunction. 1

• Measure both TSH and free T4 on repeat testing to distinguish subclinical hypothyroidism (normal free T4) from overt hypothyroidism (low free T4). 1, 2
• Consider measuring anti-TPO antibodies to identify autoimmune etiology, which predicts 4.3% annual progression risk to overt hypothyroidism versus 2.6% in antibody-negative patients. 1, 2

Treatment Algorithm Based on TSH Level

TSH >10 mIU/L: Treat All Patients

Initiate levothyroxine therapy regardless of age or symptoms when TSH exceeds 10 mIU/L. 1, 2, 5, 6 This threshold carries approximately 5% annual risk of progression to overt hypothyroidism and is associated with increased cardiovascular risk. 1

• Treatment may improve symptoms and lower LDL cholesterol, though mortality benefit remains unproven. 1
• The evidence quality for this recommendation is rated as "fair" by expert panels. 1

TSH 4.5-10 mIU/L: Individualized Approach

For TSH between 4.5-10 mIU/L, treatment decisions depend on specific clinical factors rather than TSH alone. 1, 2, 6

Treat in these specific situations:

• Symptomatic patients with fatigue, weight gain, cold intolerance, or constipation—consider a 3-4 month trial of levothyroxine with clear evaluation of benefit. 1, 2, 6
• Positive anti-TPO antibodies, which increase progression risk to 4.3% annually. 1, 2
• Women who are pregnant or planning pregnancy, as even mild TSH elevation is associated with preeclampsia, low birth weight, and neurodevelopmental effects in offspring. 1, 2, 5
• Patients with goiter or infertility. 5

Do NOT routinely treat asymptomatic patients with TSH 4.5-10 mIU/L, as randomized controlled trials show no improvement in symptoms or cognitive function with levothyroxine therapy in this range. 1, 4 Instead, monitor thyroid function tests every 6-12 months. 1

Special Considerations for Older Adults

For patients >70-80 years with TSH ≤10 mIU/L, adopt a wait-and-see strategy and generally avoid treatment. 2, 6, 4

• TSH reference ranges shift upward with age—the 97.5th percentile is 7.5 mIU/L for patients over age 80 versus 3.6 mIU/L for those under 40. 4
• Treatment may be harmful in elderly patients with subclinical hypothyroidism, while potentially reducing cardiovascular events in patients under age 65. 4
• If treatment is necessary in elderly patients, start with 25-50 mcg/day and titrate gradually to avoid cardiac complications. 1, 2

Levothyroxine Dosing Strategy

For patients <70 years without cardiac disease: Start with full replacement dose of approximately 1.6 mcg/kg/day. 1, 2, 7

For patients >70 years or with cardiac disease: Start with 25-50 mcg/day and titrate gradually every 6-8 weeks. 1, 2, 7, 3 Rapid normalization can unmask or worsen cardiac ischemia. 1

Monitoring Protocol

• Recheck TSH every 6-8 weeks while titrating until target TSH of 0.5-4.5 mIU/L is achieved. 1, 2, 7
• Once stable, monitor TSH every 6-12 months or if symptoms change. 1, 2
• Free T4 can help interpret ongoing abnormal TSH levels during therapy, as TSH may take longer to normalize. 1

Critical Pitfalls to Avoid

Never treat based on a single elevated TSH value—62% of elevated TSH levels revert to normal spontaneously. 1, 4

Overtreatment occurs in 14-21% of treated patients and increases risk for atrial fibrillation, osteoporosis, fractures, and cardiac complications, especially in elderly patients. 1, 2 Approximately 25% of patients are unintentionally maintained on doses sufficient to fully suppress TSH. 1

Do not adjust doses more frequently than every 6-8 weeks—levothyroxine has a long half-life requiring this interval to reach steady state. 1, 3

Rule out adrenal insufficiency before starting levothyroxine in patients with suspected central hypothyroidism, as thyroid hormone can precipitate adrenal crisis. 1

Recognize transient hypothyroidism (from thyroiditis, acute illness, or medications) to avoid unnecessary lifelong treatment. 1, 2