Assessment of causal association between thyroid function and lipid metabolism: a Mendelian randomization study / 中华医学杂志(英文版)

BACKGROUND@#Thyroid dysfunction is associated with cardiovascular diseases. However, the role of thyroid function in lipid metabolism remains partly unknown. The present study aimed to investigate the causal association between thyroid function and serum lipid metabolism via a genetic analysis termed Mendelian randomization (MR).@*METHODS@#The MR approach uses a genetic variant as the instrumental variable in epidemiological studies to mimic a randomized controlled trial. A two-sample MR was performed to assess the causal association, using summary statistics from the Atrial Fibrillation Genetics Consortium (n = 537,409) and the Global Lipids Genetics Consortium (n = 188,577). The clinical measures of thyroid function include thyrotropin (TSH), free triiodothyronine (FT3) and free thyroxine (FT4) levels, FT3:FT4 ratio and concentration of thyroid peroxidase antibodies (TPOAb). The serum lipid metabolism traits include total cholesterol (TC) and triglycerides, high-density lipoprotein, and low-density lipoprotein (LDL) levels. The MR estimate and MR inverse variance-weighted method were used to assess the association between thyroid function and serum lipid metabolism.@*RESULTS@#The results demonstrated that increased TSH levels were significantly associated with higher TC (β = 0.052, P = 0.002) and LDL (β = 0.041, P = 0.018) levels. In addition, the FT3:FT4 ratio was significantly associated with TC (β = 0.240, P = 0.033) and LDL (β = 0.025, P = 0.027) levels. However, no significant differences were observed between genetically predicted FT4 and TPOAb and serum lipids.@*CONCLUSION@#Taken together, the results of the present study suggest an association between thyroid function and serum lipid metabolism, highlighting the importance of the pituitary-thyroid-cardiac axis in dyslipidemia susceptibility.

Comparison of dobutamine stress echocardiography and exercise echocardiography in evaluating left ventricular outflow tract obstruction in patients with hypertrophic cardiomyopathy / 中华心血管病杂志

<p><b>OBJECTIVE</b>To compare left ventricular outflow tract (LVOT) gradient induced by dobutamine stress echocardiography (DSE) and exercise echocardiography (EE) in patients with hypertrophic cardiomyopathy (HCM).</p><p><b>METHODS</b>DSE and EE were performed in 40 consecutive patients with HCM and LVOT gradient < 50 mm Hg (1 mm Hg = 0.133 kPa) at rest. Dobutamine was administered intravenously at incremental doses of 200, 400, 600, 800 and 1200 µg/min at 5 min intervals. LVOT gradients were measured at rest, at peak exercise and during each dose of DSE.</p><p><b>RESULTS</b>LVOT gradient at rest was lower than 30 mm Hg in 36 patients and between 30 and 49 mm Hg in 4 patients. Of the 36 patients with LVOT gradient < 30 mm Hg at rest, mechanical LVOT obstruction (latent LVOTO) was evidenced in 17 patients during EE and in 18 patients during DSE and good consistency (91.7%, kappa value 0.833) was found between the two maneuvers. The provoked gradient was similar between DSE at 800 µg/min and EE at peak exercise (P = 0.181). In the 4 patients with LVOT gradient between 30 and 49 mm Hg [(38.8 ± 2.6) mm Hg], LVOT gradient increased to (85.3 ± 26.4) mm Hg during EE and (105.0 ± 28.0) mm Hg during DES.</p><p><b>CONCLUSIONS</b>DES and EE are comparable and suitable provoke methods for identifying LVOT obstruction in patients with HCM.</p>