Endocrine Abstracts

: Two-way interactions between thyroid and kidney functions are known. Chronic kidney disease (CKD) is accompanied by changes in synthesis, secretion, metabolism, and elimination of thyroid hormones, increased risk of hypothyroidism, rarely subclinical hyperthyroidism, whereas thyroid dysfunction affects physiology of the kidney, renal blood flow, glomerular filtration rate (GFR), tubular function, metabolism of water and electrolytes, and kidney structure. The aim of the study was to examine associations between thyroid stimulating hormone (TSH) level and kidney function.

Methods: We analysed retrospective data of 781 adult patients, referred for routine simultaneous testing of TSH and serum creatinine in 2015 in Vilnius Antakalnio outpatient clinic. GFR was estimated by the simplified Modification of Diet in Renal Disease equation. Linear regression was used to evaluate the association between TSH and estimated GFR.

Results: Mean TSH concentration was 2.58±4.19 mIU/l, mean serum creatinine 72.72±22.32 μmol/l and mean estimated GFR 83.12±24.91 ml/min/1.73 m². 45.3% of patients had stage 2 CKD, 16.0% – stage 3 CKD, 1% – stage 4 or end stage CKD. Patients with CKD of any stage were older than those with normal kidney function (mean age 66.98±11.20 vs 50.96±15.42 years, P<0.0001) and their TSH was higher (2.86±5.07 vs 2.12±1.93 mIU/l, P=0.004). 12.9% of patients had thyroid dysfunction: 7.9% had subclinical hypothyroidism (TSH 4.69–10 mIU/l), 1.3% overt clinical hypothyroidism (TSH >10 mIU/l) and 3.7% subclinical hyperthyroidism (TSH <0.465 mIU/l). 12.8% of patients with estimated GFR <60 ml/min/1.73 m² had subclinical hypothyroidism, 1.5% – overt clinical hypothyroidism. Lower estimated GFR was associated with higher TSH level (B=−0.72 (95% CI −1.13 – −0.30), P=0.001).

Conclusions: Thyroid dysfunction is relatively common among persons with CKD: 14.3% of patients with moderate, severe and established kidney failure have hypothyroidism. Reduction in estimated GFR is independently associated with increased TSH levels.