Thyroid Dysfunction

The prevalence of chronic kidney disease (CKD) in China was 10.8%. Clinically, disorders of the thyroid gland such as hypothyroidism and euthyroid sick syndrome (ESS) often occur in CKD patients; especially in CKD stage 5. Patients with hypothyroidism can have clinically important reductions in estimated glomerular filtration rate (eGFR); which can attenuate by using thyroid hormone replacement therapy.

Hypothyroidism can also lead to hyperlipidemia and atherosclerosis in coronary and peripheral vessels. Studies indicated that subclinical and clinical hypothyroidism were the risk factors for all-cause mortality and CVD death. Similar to hypothyroidism, ESS was with endothelial dysfunction in stage 3 and 4 CKD patients; as well as with cardiomyopathy and a high risk of death in CKD stage 5.

The subclinical primary hypothyroidism

A study has indicated that the prevalence of subclinical primary hypothyroidism increased from 5.4% at an estimated GFR >90 mL/min/1.73 m2 to more than 20% at an estimated GFR <60 mL/min/1.73 m2. In addition, Song and his fellows showed high morbidity of low T3 in CKD patients. However, the mechanistic link and directionality of the association between ESS and kidney disease remain widely unknown.

It is well known that CKD can induce a number of complications and comorbidities. No data to date are available about the relationships of thyroid hormone and eGFR, gender, age, uric acid, hemoglobin (Hb), albumin, and C-reactive protein (CRP) in CKD patients. Hence, they conducted the study to explore the relationships between thyroid hormone and biomarkers in CKD patients and ascertain risk factors for ESS.

A total number of 905 non-dialysis participants were collected at Nanjing First Hospital from August 2009 to October 2012 according to the case records system. Patients grouped via the estimated glomerular filtration rate (eGFR), but according to the KDIGO guideline. Levels of thyroid hormone and biomarkers in different CKD groups compared by ANOVA. Prevalence of different thyroid diseases was calculated by χ2 test.

Euthyroid sick syndrome

Therefore they found that FT3 or T3 became more prevalent with increasing eGFR with the lowest level in CKD5 (p < 0.01). No significant differences found between groups in FT4, T4, or TSH (p > 0.05). Frequency of euthyroid sick syndrome (ESS) in CKD groups was high, especially in CKD stage 5 (69.1%, p < 0.01). eGFR had positive correlation with T3 and FT3 (r = 0.239, p = 0.0001; r = 0.292, p = 0.0001).
In conclusion, ESS had correlations with prealbumin, β2-microglobulin, eGFR, and C-reactive protein. After adjustment for prealbumin, uric acid, HbA1c, age, gender, eGFR, and β2-microglobulin, binary regression revealed that hemoglobin, C-reactive protein, and albumin were independent influence factors of ESS (p = 0.016, r = 1.014; p = 0.023, r = 1.007; p = 0.029, r = 0.996). Conclusion: CKD patients have high morbidity of ESS, mainly low T3 syndrome. Anemia, inflammation, and malnutrition may contribute to ESS in CKD.