The Thyrotropin Reference Range Should Remain Unchanged

Context: Recent recommendations to decrease the upper limit of the TSH reference range from 4.5 to 2.5 mIU/liter, based on the high proportion of normal people whose serum TSH is less than 2.5 mIU/liter and the observation that those with TSH between 2.5 and 4.5 mIU/liter [upper reference range (URR)] have increased risk of progression to overt hypothyroidism (Whickham, 20-yr data), have not been subjected to critical...