Diagnosis and Management of Hashimoto's Thyroiditis

Initial Laboratory Testing

The American Academy of Family Physicians recommends measuring TSH as the primary screening test when Hashimoto's thyroiditis is suspected, with sensitivity above 98% and specificity greater than 92% 1, 2
Measuring both TSH and free T4 (FT4) simultaneously is necessary to distinguish between different thyroid states, including overt hypothyroidism, subclinical hypothyroidism, and euthyroid status 3, 4

For patients with elevated TSH and positive TPO antibodies, treatment consideration is necessary, as this confirms Hashimoto's thyroiditis with hypothyroidism 5
The American College of Physicians suggests initiating levothyroxine therapy in patients with elevated TSH >10 mIU/L, as this level carries approximately 5% annual risk of progression to overt hypothyroidism 5
For patients with TSH 4.5-10 mIU/L, treatment should be considered if symptomatic or if positive TPO antibodies are present, given the higher progression risk 5

In pregnant or postpartum women, untreated maternal hypothyroidism increases the risk of preeclampsia and low birth weight, making screening and treatment crucial 1, 2
Positive TPO antibodies identify patients at higher risk of progression to overt hypothyroidism, with a rate of 4.3% per year versus 2.6% per year in antibody-negative individuals 5