Subclinical hypothyroidism

• Mild ↑ TSH and
  • normal free T4 with only subtle or no sx
• If TSH <7 or ⊖ anti-TPO Ab, ~½ resolve after 2 y (JCEM 2012;97:1962)
• if ↑ titers of antithyroid Abs, progression to overt hypothyroidism is ~4%/y
• No clear benefit to Rx (NEJM 2017;376:2534).
• In practice, follow expectantly or Rx to improve mild sx or dyslipidemia.
• Experts often Rx if TSH >10 mU/L, goiter, pregnancy or infertility.