TSH thresholds defined

TSH cutoffs of 2.5 and 4.0 mU/liter combined with thyroid antibodies provide a clinically useful estimate of the long-term risk of hypothyroidism, researchers from Western Australian report. The study of over 1,000 Busselton Health Survey participants found that while individuals with serum TSH within these limits had an increased risk of hypothyroidism, the majority did not develop hypothyroidism by 13 year follow-up. “It is for this reason we do not support lowering the upper limit of the TSH reference range to 2.5 mU/liter, but it is certainly reasonable to regard TSH concentrations of 2.5-4mU/liter as a category of intermediate risk, especially in women with positive thyroid antibodies,” they said....