#1080 Low-T3 syndrome: “endemic” in hemodialysis patients?
Authors: Cacciapuoti Martina , Cuva Gianluca , Lorenzo Calò 
Published: May 2024

Abstract

Background and Aims
In hemodialysis patients, low-T3 syndrome is more prevalent than in the general population and was found to be associated with malnutrition and inflammation. Although evidence suggest that low free T3 (fT3) levels predict cardiovascular and all-cause mortality, low-T3 syndrome is usually not treated.
The aim of this single-center retrospective observational study was to determine the prevalence of thyroid axis derangements and examine the relationship between thyroid hormones and biochemical and clinical variables in our hemodialysis (HD) patients cohort.

Method
Patients on thrice-weekly maintenance HD for at least 6 months were enrolled. Patients taking amiodarone, levothyroxine or methimazole were excluded. Data about age, sex, ethnicity, hemodialysis vintage, type of dialysis (bicarbonate dialysis/online hemodiafiltration/acetate-free-biofiltration/hemofiltration with endogenous reinfusion/expanded hemodialysis) were obtained from medical records and values of fT3, fT4, TSH, albumin, LDL, hemoglobin—routinely checked for every patient during hemodialysis sessions—were acquired.
Continuous variables are expressed as median and IQR or mean ± SD and categorical variables as absolute value or percentage. The normality of data distribution was tested by Sapiro-Wilk test. Correlations were studied with Pearson and Spearman. T-test and Mann-Whitney U test were performed to compare continuous and categorical variables. Statistical significance was reached with p &lt; 0.05.

Results
A total of 57 patients on thrice-weekly maintenance HD were enrolled. Most of them were male (70.2%), Caucasians (89.5%), with a mean age of 69 ± 14 years and with a median dialytic vintage of 63 [29; 113] months. Hypertension was the most frequent comorbidity and more than half of the patients was either affected by ischemic, hypertensive or dilatative cardiomyopathy. Most of the patients underwent bicarbonate hemodialysis (42.1%) and overall 57.9% of the study population was treated by convective techniques. Hemoglobin, albumin, LDL cholesterol, fT3 and fT4 values was normally distributed, while those of TSH and PCR were not.
A very high prevalence of low-T3 syndrome (75%) was found, 5 patients showed subclinical hypothyroidism and only in a minority of patients thyroid function tests were normal (12%) (Fig. 1).
A significant negative correlation between fT3 and age (p = 0.041) and a positive one between TSH and dialytic vintage (p = 0.017) were found (Table 1).
In addition, a significant positive correlation between albumin and fT3 was detected, supporting the known association between low T3 and malnutrition. Interestingly, PCR negatively correlated with fT3 and positively with fT4.
Patients treated by diffusive techniques showed no statistically significant difference of thyroid hormone levels compared to convective therapies (Table 1).

Conclusion
Low-T3 syndrome affects the great majority of patients in our hemodialysis population, with a prevalence even higher than that provided by literature.
Our investigations confirm that older patients seem to show lower fT3 levels and a longer hemodialysis vintage may correlate with higher TSH levels. The association with inflammation was also confirmed.
Considering the known impact on cardiovascular and all-cause mortality already demonstrated, it is important to routinely check thyroid hormones in HD. In addition, further studies should be performed in order to establish the possible impact of the therapeutic correction of this hormonal derangement on hemodialysis patients’ mortality and cardiovascular outcomes.