Relationship between serum level of thyroid hormones and plasma level of N-terminal Pro-brain natriuretic peptide in elderly patients with type 2 diabetes

Abstract

Objective To investigate the relationship between thyroid function indexes and plasma level of N-terminal pro-brain natriuretic peptide (NT-proBNP) among patients who had high risks for cardiovascular diseases without thyroid diseases and heart failure. Methods Totally 166 elderly type 2 diabetic patients aged 80 years and over with normal range of thyroid stimulating hormone (TSH) were divided into group of euthyroid sick syndrome (ESS, n=62) and group of normal thyroid hormones (NESS, n=104). The patients in normal thyroid hormones group were divided into three subgroups according to the levels of total triiodothyronine (TT3), (low-level group, n=26; middle-level group, n=50; high-level group, n=28). Levels of thyroid hormones, NT-proBNP, cholesterol, low-density lipoprotein cholesterol, fibrinogen, HbA1C, glomerular filtration rate (eGRF), left ventricular ejection fraction (LVEF) and the incidences of concomitant diseases were measured and detected. lgNT-proBNP was used to calculated after NT-proBNP was changed by Log transformation. Results Compared with NESS group, ESS group showed that age was increased, systolic pressure and LVEF were decreased 〔(86.3±5.8) years vs. (85.6±5.2) years, (126.6±15.5) mmHg vs. (135.6±17.8) mmHg, (63.9±7.6)% vs. (67.4±7.5)%, all P<0.01〕. Compared with NESS group, ESS group showed that the levels of serum total T3 and free T3 were decreased 〔(0.89±0.17) nmol/L vs. (1.45±0.31) nmol/L, (3.31±0.55) pmol/L vs. (3.96±0.59) pmol/L, both P<0.01〕. The lgNT-proBNP level was higher and serum total thyroxine (TT4) level was lower in ESS group than in NESS group 〔(2.40±0.40) ng/L vs. (2.26±0.44) ng/L, (101.80±36.11) nmol/L vs. (111.07±23.29) nmol/L, both P<0.05〕. Pearson analysis revealed that serum levels of TT3, TT4 and FT3 were negatively correlated with lgNT-proBNP (r=-0.217, -0.180, -0.174, respectively, all P<0.05) after adjustment for age, systolic pressure and LVEF. Stepwise regressive analysis showed TT3 was the risk factors for lgNT-proBNP (β=-0.267, P<0.01). Compared with the low-level group, the lgNT-proBNP were significantly reduced in the middle-, and high-level groups 〔(2.19±0.42) ng/L, (2.19±0.46) ng/L vs. (2.44±0.39) ng/L, both P<0.05〕. Conclusions TT3 has a close correlation with NT-proBNP in elderly type 2 diabetic patients with normal TSH. It has a significant meaning to test TT3 level for monitoring heart function in clinical medicine. Key words: Euthyroid sick syndromes; Thyroid hormones; Natriuretic peptide, brain; Diabetes mellitus, type 2