The Whickham survey study conducted by Vanderpump and Co. over 20 years on healthy volunteers concludes that: "More than 95% of the euthyroid patients (normal thyroid function) had TSH levels between 0.4 and 2.5 mIU/L, but among this cohort, those with first TSH levels higher than 2 mIU/L had much higher risk of developing a hypothyroidism within the following 20 years, and particularly those with high thyroid antibodies".
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