Importance of specific reference values for evaluation of the deteriorating thyroid function in patients with...

We evaluated the thyroid function in end-stage renal disease (ESRD) on maintenance hemodialysis.

Thyroid function and clinical hypothyroid score were evaluated in 145 ESRD patients.

Comparison of thyroid function between 127 ESRD patients, excluding 18 patients with suppressed or elevated serum TSH level, and age/sex-matched healthy controls (76 in midlife group aged under 65 and 51 in late-life group aged 65 or over) using a multivariate logistic regression analysis suggested significant difference (P < 0.0001), mainly in serum fT4 level (P = 0.0099) and age (P = 0.0492), but not in serum fT3 (not significant; ns), TSH (ns) level or fT3/fT4 ratio (ns). Serum fT3 level and fT3/fT4 ratio were significantly lower (P < 0.001) in late-life group only in ESRD. Reference values calculated for midlife ESRD patients, such as 0.6-1.3 ng/dl for fT4 compared with 0.8-1.7 ng/dl for healthy control, were helpful for the diagnosis of mild but definite hyperthyroidism in whom serum fT4 level was 1.5 ng/dl. The prevalence of primary thyroid dysfunction, compared with the values for ESRD, was 0.7 % for hyperthyroidism, 1.4 % for overt hypothyroidism and 10.3 % for subclinical hypothyroidism. Hypothyroid score was high among those with ESRD independent of thyroid dysfunction.

Serum fT4 level was markedly lower without a change in fT3/fT4 ratio in ESRD. This may suggest typical carbohydrate-sufficient non-thyroidal illness. The specific reference values for ESRD were useful to evaluate borderline thyroid dysfunction and to evaluate the prevalence of the patients with primary thyroid dysfunction in ESRD.