Abstract: Objective To investigate the relationship between thyroid hormones (TH) and residual urine volume (RUV) and their reciprocal influences in maintenance hemodialysis (MHD) patients. Methods We recruited 79 MHD patients treated twice a week for more than 12 months in the period from Oct. 2012 to Oct.
2014 in our hospital. Their clinical parameters including RUV and TH were collected. They were then divided into two groups based on RUV: RUV group (RUV ＞100ml/d, n=22) and NRUV group (RUV ＜100ml/d, n= 49). Clinical parameters were compared between the two groups. Factors influencing RUV were analyzed by using multivariate logistic regression. The relationship between TH and RUV was evaluated. The RUV group was further divided into two subgroups based on free triiodothyronine (FT3): subgroup A (FT3 ＞3.8 pmol/l) and subgroup B (FT3 ≤3.8 pmol/l). The two subgroups were followed up for one year (48 weeks), and the end points was the event of RUV ＜100ml/d. The probability difference about the occurrence of end points was evaluated by using Kaplan- Meier method. Results A total of 71 MHD patients with RUV of 70(130) ml were enrolled in this study. FT3 was 3.67±0.56 pmol/l in these patients, including 43 patients (60.6%) with lowered FT3. FT4 was 8.65(1.5) pmol/l in these patients, including 8 patients (11.3%) with lowered FT4. Six patients (8.5%) had both lowered FT3 and FT4. Seventy-one patients were assayed for TSH, and they were all normal. In RUV group, dialysis vintage was shorter (1.75±2.03 vs. 4.23± 2.89 years; t=-4.153, P＜0.001), FT3 was higher (3.87±0.41 vs. 3.58±0.54 pmol/l; t=2.444, P=0.018), Kt/V was higher (1.27±0.06 vs. 1.23±0.08; t=2.183, P= 0.032), PTH was lower [181.95(244.35) vs. 324.0(370.8) pg/ml; z=2.102, P=0.036], and the occurrence of interdialytic hypotension was lower [0.024(0.073) vs. 0.097(0.150); z=2.166, P=0.030], as compared with those in NRUV group. Multivariate logistic regression found that FT3 and dialysis vintage were correlated
significantly with RUV (B=1.983, P=0.002 for FT3; B=-0.388, P=0.007 for dialysis vintage). Spearman rank partial correlation analysis revealed that FT3 was positively correlated with RUV (R=0.603, P＜0.001) after excluding the factor of dialysis vintage. In the follow-up period we found that RUV decreased frequently
in the B subgroup of RUV group (χ2=9.748, P=0.002). Conclusions FT3 and dialysis vintage were significantly correlated with RUV in MHD patients. Clinically, we should pay attention to the change of FT3 in MHD patients.

Key words: maintenance hemodialysis, residual urine volume, thyroid hormones