1994 Volume 27 Issue 10 Pages 1313-1318
Thyroid function in hemodialysis (HD) patients is generally considered to be normal in spite of low serum thyroid hormone levels. It is well known that assay of free T4 (FT4) by conventional RIA based on labelled T4 analogue (AN-RIA) shows relatively low levels because of interference by serum proteins, such as albumin and T4 binding globulin (TBG), in HD patients. In this study, we examined FT4 levels in HD patients using a newly developed equilibrium dialysis radioimmunoassay (ED-RIA), and made a comparison with AN-RIA.
Serum FT4 levels in 32 patients with chronic renal failure just before the first HD, 118 patients on maintenance HD and 43 normal healthy controls were assessed by AN-RIA and ED-RIA. By AN-RIA, 16 out of 32 patients (50%) just before the first HD and 34 out of 118 (29%) on maintenance HD were within normal range. However, by ED-RIA, 29 out of 32 (91%) and 98 out of 118 (83%) were within normal range, respectively. There was no significant correlation between FT4 by ED-RIA and either serum albumin or TBG. There was a good correlation between ED-RIA and AN-RIA (r=0.636). We also measured FT4 in HD patients with permanent or transient hypothyroidism due to Hashimoto's thyroiditis or iodine excess. The values by ED-RIA yielded reasonable results reflecting TSH secretion and clinical course. In conclusion, ED-RIA is very useful for measuring serum FT4 in the assessment and monitoring of thyroid function during the clinical course in HD patients.
