Serum substances that interfere with thyroid hormone assays in patients with chronic renal failure

• Published in: Clinical endocrinology (Oxford) 1998-06, Vol.48 (6), p.739-746
• Main Authors: Iitaka, Makoto, Kawasaki, Satomi, Sakurai, Shin-ichi, Hara, Yoshihito, Kuriyama, Renjiro, Yamanaka, Kayo, Kitahama, Shinji, Miura, Shiro, Kawakami, Yoshito, Katayama, Shigehiro
• Format: Article
• Language: English
• Subjects: Aged; Biological and medical sciences; Chromatography, High Pressure Liquid; Endocrinology; Female; Hippurates - blood; Humans; Indican - blood; Indoleacetic Acids - blood; Investigative techniques, diagnostic techniques (general aspects); Kidney Failure, Chronic - blood; Kidney Failure, Chronic - therapy; Male; Medical sciences; Middle Aged; Pathology. Cytology. Biochemistry. Spectrometry. Miscellaneous investigative techniques; Radioimmunoassay; Radioligand Assay; Regression Analysis; Renal Dialysis; Sensitivity and Specificity; Thyroid Hormones - blood; Thyroxine - blood; Triiodothyronine - blood
• ISSN: 0300-0664; 1365-2265
• DOI: 10.1046/j.1365-2265.1998.00419.x

OBJECTIVE Serum thyroid hormone concen_trations in patients with chronic renal failure are usually low, despite normal serum TSH levels. We investigated the effect on thyroid hormone assays of serum dialysable organic acids that are elevated in uraemic patients. PATIENTS Serum samples from 42 patients with chronic renal failure who were receiving haemodialysis and 37 sex‐ and age‐matched healthy subjects were examined. DESIGN AND MEASUREMENTS Serum thyroid hormone concen_trations were measured with an analogue radioimmunoassay (RIA), a labelled antibody assay, and an equilibrium dialysis/RIA method. Serum concen_trations of organic acids were determined with high performance liquid chromatography. RESULTS Serum thyroid hormone levels determined by an analogue RIA and a labelled antibody assay in uraemic patients increased, and serum concen_trations of organic acids decreased following haemodialysis. A significant association existed between serum free T3 (FT3) levels determined by an analogue RIA and serum concen_trations of indoxyl sulphate (IS) prior to dialysis. There was also a significant association between serum free T4 (FT4) levels determined by an analogue RIA and serum concen_tration of IS and hippuric acid (HA) prior to dialysis. There was a significant association between the changes of serum concen_trations of indole acetic acid (IAA) and FT4 concen_trations prior to and following haemodialysis when determined by an analogue RIA. Serum FT3 and FT4 levels significantly decreased after the addition of IS to serum from healthy subjects when determined by an analogue RIA but not by a labelled antibody assay. Serum FT4 levels, but not FT3 levels, decreased after addition of IAA when determined by an analogue RIA. Serum FT4 concen_trations determined by an equilibrium dialysis/RIA were significantly higher than those determined by the other two methods. The addition of IS, IAA, and HA to serum samples from healthy subjects significantly increased FT4 concen_trations when determined by an equilibrium dialysis/RIA method. CONCLUSIONS Increased serum levels of indoxyl sulphate, indole acetic acid and hippuric acid in sera of uraemic patients may interfere with thyroid hormone measurements when an analogue radioimmunoassay is used. In contrast, there was little interference with a labelled antibody assay. Dialysable organic acids may also interfere with thyroid hormone assays determined by an equilibrium dialysis/radioimmunoassay method.