Thyroid Function and Antibody Testing Guidelines (Endocrine Practice)
Core Thyroid Function Tests
- TSH measurement is the primary test for assessing thyroid status and should always be ordered together with antibody testing – American College of Endocrinology & American Association of Clinical Endocrinologists 1, 2
- Free T4 (instead of total T4) should be measured in non‑pregnant patients to obtain an accurate assessment of circulating thyroid hormone – American College of Endocrinology & American Association of Clinical Endocrinologists 1, 2
- In pregnant patients, total T4 or a free T4 index should be used together with TSH because free T4 assays show wide variation during pregnancy – American College of Endocrinology & American Association of Clinical Endocrinologists 2, 3
Antibody Testing in Specific Clinical Scenarios
- TSH‑receptor antibodies (TRAb) should be measured in pregnant individuals with a history of Graves’ disease treated by radioactive iodine or thyroidectomy; testing is recommended in the first trimester and repeated at 20–26 weeks if the initial result is elevated – American College of Endocrinology & American Association of Clinical Endocrinologists 1, 3, 4
- Anti‑thyroid peroxidase antibodies (TPOAb) in patients with subclinical hypothyroidism predict progression to overt hypothyroidism at approximately 4.3 % per year when positive versus 2.6 % per year when negative – American College of Endocrinology & American Association of Clinical Endocrinologists 1, 2
- TPOAb testing is indicated in individuals with recurrent miscarriage (with or without infertility) to evaluate an autoimmune contribution – American College of Endocrinology & American Association of Clinical Endocrinologists 1, 3
- When nodular thyroid disease is present and autoimmune thyroiditis is suspected, TPOAb measurement helps clarify the underlying etiology – American College of Endocrinology & American Association of Clinical Endocrinologists 1, 2
Tests Not Recommended for Routine Diagnosis of Hypothyroidism
- Cholesterol, muscle‑enzyme, and reflex‑relaxation‑time measurements lack diagnostic utility for hypothyroidism and should not be ordered routinely – American College of Endocrinology & American Association of Clinical Endocrinologists 1, 2, 3
- Clinical scoring systems are not appropriate for diagnosing hypothyroidism – American College of Endocrinology & American Association of Clinical Endocrinologists 1, 3