The influence of hypothyroidism and substitution treatment on thyroid hormone conversion ratios and rT3 concentration in patients with end-stage renal failure

Introduction: The increasing number of patients with end-stage renal disease (ESRD) requires seeking new opportunities to improve their quality of life, not only because of kidney disease but also due to other disturbances, such as thyroid hormone disorders. The objective of the study was to evaluate the influence of coexisting hypothyroidism and thyroid hormone therapy in patients with ESRD on thyroid hormone conversion ratios and rT3 concentration. Material and methods: The study involved 85 patients aged 26 to 87 years, with a mean age of 59.62 ± 15.45 years. Four groups of patients were examined: G1 group — 25 persons without RF and hypothyroidism, G2 — 26 patients with ESRD treated with haemodialysis (HD), G3 — 12 patients with ESRD treated with HD and newly diagnosed hypothyroidism, and G4 — 22 HD patients with hypothyroidism treated with thyroid hormones substitution. The concentrations of TSH, T4, T3, fT4, fT3, and rT3 were measured and the fT3/fT4, T3/T4, and rT3/T4 conversion ratios and rT3/T3 ratio were calculated. Concentrations of protein, hsCRP, Hg, and blood gases were also checked; the anion gap was calculated. Results: Patients from group G1 through G2 to G3 were older (p trend = 0.002), with lower Hb level (p trend < 0.001), with lower pH (p trend < 0.001), with increased anion gap (p trend < 0.013) and CRP concentrations (p trend < 0.001), and decreased total protein level (p trend < 0.001). There were increased TSH values (p trend < 0.001) and lower T4 (p trend = 0.024), fT3 (p trend < 0.001), T3 (p trend < 0.001), and rT3 (p trend = 0.008) levels. rT3/T3 ratio did not change, the rT3/T4 ratio tended to decrease (p trend = 0.065) similarly to T3/T4 ratio (p trend = 0.063), and the fT3/fT4 ratio also decreased (p trend = 0.005). It seems that the treatment of thyroid disease in patients with renal failure, treated with haemodialysis, is not associated with change of rT3 and conversion factor levels. Conclusions: The concentration of rT3 in HD patients in relation to healthy persons tends to decrease, and hypothyroidism increases this tendency in these patients. Hormone substitution treatment does not eliminate the influence of RF on inhibition of rT3 production. In patients with ESRD, hypothyroidism additionally reduces the conversion of thyroid hormones examined by fT3/fT4 and to a lesser extent T3/T4 ratios.