Effects of Hemodialysis on the Serum Thyroid Hormone and TSH Levels

Serum levels of free T₃（FT₃）, free T₄（FT₄）, total T₃（TT₃）, total T₄（TT₄） and TSH_IRLA were measured in 43 and 67 normal subjects, 35 uremic patients （conservative 14, hemodialysis ones 21）. Significamly lowered mean serum FT₃, FT₄ and TT₃ but normal T₄ and TSH_IRMA were observed in untreated uremic and hemodialysis ones, although all the subjects were euthyroid. The rates of low FT₃, FT₄, TT₃ and TT₄ were 37.5, 42.9, 50 and 21% in conservative uremic patients and 81, 38.1, 61.9 and 14.2% in hemodialysis patients respectively. The postdialysis TSH_IRMA level was significantly reduced and FT₃, FT₄, TT₃ and TT₄ were unchanged after transient hemodialysis. There was no change of the rates of low FT₃, FT₄, TT₃ and TT₄ in the couse of maintained dialysis.
The conclusion is that FT₃, FT₄, TT₃ and TT₄ are lowered in parts of conservative uremic and hemodialysis patient but TSH_IRMA is normal or only slightly low. The thyroid function of them is most likely normal （euthyroid）. TSH_IRMA is a useful index in diagnosing hypothyroidism in uremic and hemodialysis patients. Transient and maintained hemodialysis do not dramaticaly change the thyroid hormone and TSH_IRMA levels.