We enrolled 241 patients who were diagnosed with overt hyperthyroidism between May 2018 and May 2019 in the inpatient department of endocrinology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China. As defined in the guidelines of the American Thyroid Association Guidelines, overt hyperthyroidism was defined as increased free thyroxine (FT4) and/or free triiodothyronine (FT3) level and a concomitantly suppressed thyroid-stimulating hormone (TSH) level. HHD was diagnosed in patients with overt hyperthyroidism with at least one of the following cardiac abnormalities: arrhythmia (e.g., atrial fibrillation, paroxysmal supraventricular tachycardia, frequent ventricular premature beat, conduction block, etc.), heart failure, cardiac dilatation, angina pectoris or MI and valve prolapse with pathological murmur in the cardiac auscultation area[21, 22]. In addition, patients with cardiac disease secondary to other etiologies should be excluded.
We excluded subjects with conditions, including tumor, sepsis, severe injury, diabetes mellitus, hyperlipidaemia, atherosclerosis, chronic renal failure and fibrosis-associated disease, known to be associated with an increased circulating CTGF level. In addition, we excluded patients with a history of surgery within 6 months prior to admission.
Blood sampling and measurement of CTGF
Venous blood samples were drawn into collection tubes containing EDTA in the morning of the second day following the admission and after at least 8 hours overnight fasting. The plasma was separated from blood cells within 2 hours of sample collection by centrifugation at 2500 g for 15 minutes at room temperature, and pipette out and frozen at -80°C until the assay with an ELISA kit.
Medical data collection of subjects
Data on the demographic characteristics, physical examinations, routine biochemical marker, thyroid function tests, radioactive iodine uptake test and 99mTc sodium pertechnetate thyroid uptake test were recorded, including age, sex, weight, height, heart rate, blood pressure, duration of symptoms of hyperthyroidism, estimated thyroid mass and the levels of total bilirubin (TBIL), aspartate aminotransferase (AST), alanine aminotransferase (ALT),serum albumin (ALB), gamma-glutamyl transpeptidase (GGT), alkaline phosphatase (ALP), uric acid (UA), creatinine (Cr), blood uric nitrogen (BUN), triglyceride (TG), total cholesterol (TC), low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C), fasting plasma glucose (FPG), serum electrolytes (i.e., sodium, potassium, calcium, phosphorus, magnesium), BNP, creatine kinase (CK), creatine kinase-MB (CK-MB), cardiac troponin I (TnI), lactate dehydrogenase (LDH), TSH, FT4, FT3, anti-thyroglobulin antibody (TGAb), anti-thyroid peroxidase antibody (TPOAb), thyrotropin receptor antibody (TRAb), and 2-hour and 24-hour radioactive iodine (131I) uptake (RAIU). The body mass index (BMI) was calculated as the weight (kg) divided by height (m) squared.
A complete transthoracic echocardiography (TTE) was undertaken in all participants by using an ultrasonographic system with a 3~8 MHz transducer (GE Vivid 7; Vingmed; Philips EPIQ 7C and Philips IE33), in accordance with the recommendations of the American Society of Echocardiography. All examinations were conducted and analyzed by an experienced operator who was unaware of the patients’ clinical status. The following parameters were recorded on TTE: the ascending aorta diameter (AAOD), left ventricular end-diastolic diameter (LVEDD), interventricular septum thickness (IVST), right ventricular end-diastolic diameter (RVEDD), right left atrium diameter (LAD), atrium diameter (RAD), pulmonary artery diameter (PAD); left ventricular ejection fraction (LVEF). In addition, the peak velocities of the early (E-wave) (MVE) and late (A-wave) (MVA) phase of the mitral inflow pattern were measured from an apical four-chamber view. Moreover, we ascertained whether the patients had pulmonary hypertension (PH), left ventricular (LV) diastolic dysfunction and valvular regurgitation according to the recommendations[24-26]. The pulmonary arterial systolic pressure was estimated from the sum of the tricuspid regurgitation maximal velocity and estimated right atrial pressure by using the simplified Bernoulli equation. PH was defined as a mean pulmonary artery that was greater than or equal to 25 mm Hg. LV diastolic dysfunction was defined by the mitral E/A ratio or septal basal regions e/a ratio less than 1. Color flow doppler was used for the detection of valvular regurgitation.
All statistical analyses were conducted with SPSS 22.0 (SPSS, Chicago, Illinois, USA). The Kolmogorov-Smirnov test was conducted to confirm whether the continuous variables conformed to normal distribution. The patients’ data were expressed as mean ± standard deviation (SD) for normally distributed data and median (interquartile range [IQR] 25th–75th percentile) for data with skewed distribution data. All categorical variables were presented as numbers (proportions). The intergroup differences were analyzed by the Student’s t-test, the Mann-Whitney test, or the Chi-square test, as appropriate. Spearman’s correlation analysis was undertaken to explore the associations between the CTGF level and thyroid-related and echocardiography parameters. A binary logistic regression analysis was conducted to identify odds ratios (OR) and 95% confidence intervals (CI) of HHD by quintiles of the plasma CTGF levels. Additionally, potential confounders were controlled. All tests were two-sided, and P-values < 0.05 were considered statistically significant.