“W D Fraser, “E M Biggart, “D S O’Reilly, “H W Gray, J H McKillop, and J A Thomson.Are biochemical tests of thyroid function of any value in monitoring patients receiving thyroxine replacement? Br Med J (Clin Res Ed). 1986 September 27; 293(6550): 808810.
AbstractThe development and application of free thyroid hormone assays’ and sensitive thyroid stimulating hormone assays during the past five years has led to the reappraisal of the best biochemical tests of thyroid function in different disease states. There is considerable controversy over which tests should be used to monitor patients receiving thyroxine replacement for primary hypothyroidism, in whom the detection of over-replacement poses a problem. Different authors have claimed that over-replacement is best detected by measuring the serum concentration of total thyroxine,’ total triiodothyronine, 4 free thyroxine,’ or free triiodothyronine. The value of some of these tests has been questioned, while others have recommended measuring both thyroid stimulating hormone, using a sensitive method, and free triiodothyronine. Euthyroid patients receiving thyroxine replacement have higher serum thyroxine and free thyroxine concentrations than normal euthyroid subjects. This is not so for serum triiodothyronine and free triiodothyronine concentrations.