What is the normal TSH range?

The standard reference range is 0.4-4.0 mIU/L, though many endocrinologists use 0.5-3.0 mIU/L for optimal thyroid function. The range shifts with age: elderly patients often have higher TSH levels (up to 7-8 mIU/L) without clinical hypothyroidism.

What are the TSH targets in pregnancy?

ATA 2017 guidelines: first trimester 0.1-2.5 mIU/L; second trimester 0.2-3.0 mIU/L; third trimester 0.3-3.0 mIU/L. These tighter ranges reflect the increased thyroid demand of pregnancy and importance of adequate maternal thyroid hormone for fetal brain development.

When is TSH unreliable for diagnosing thyroid disease?

TSH is unreliable in central hypothyroidism (pituitary/hypothalamic disease), sick euthyroid syndrome (acute illness suppresses TSH), during the first trimester of pregnancy, and with dopamine or glucocorticoid use, which suppress TSH.

TSH Interpretation Zones

Interpret TSH levels: <0.4 mIU/L hyperthyroid (or over-replacement), 0.4-4.0 euthyroid (normal), 4.0-10.0 subclinical hypothyroid, >10.0 overt hypothyroid. Pregnancy targets 0.1-2.5 first trimester.

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Frequently Asked Questions

What is the normal TSH range?

What are the TSH targets in pregnancy?

When is TSH unreliable for diagnosing thyroid disease?