Establishment of assay method- and trimester-specific reference intervals for thyroid hormones during pregnancy in Chengdu, China.

BACKGROUND: The reference intervals of thyroid hormone will change at different stages of pregnancy because of physiological alterations. On the other hand, the reference intervals of thyroid hormone will also change in different detection systems due to the manufacturer's methodology as well as a different race. The objective of this study was to establish the assay method- and trimester-specific reference intervals for thyroid-stimulating hormone, free thyroxine and free triiodothyronine for pregnant women in Chengdu. METHODS: A prospective, population-based cohort study involved 23,701 reference samples of pregnant women during the three trimesters and 8646 non-pregnant women with pre-pregnancy clinical and laboratory tests. The 2.5th and 97.5th percentiles were calculated as the reference intervals for thyroid-stimulating hormone, free thyroxine and free triiodothyronine at each trimester of pregnant women according to ATA Guidelines. RESULTS: The reference interval of thyroid-stimulating hormone in the 2.5th and 97.5th percentiles has a significant increasing trend from the first trimester, to second trimester and to third trimester, which was 0.08-3.79 mIU/L for the first trimester, and 0.12-3.95 mIU/L for the second trimester and 0.38-4.18 mIU/L for the third trimester, respectively (p < 0.001). However, the reference intervals of free thyroxine and free triiodothyronine in the 2.5th and 97.5th percentiles have significant decreasing trends from the first trimester, to second trimester and to third trimester, which were 11.87-18.83 pmol/L and 3.77-5.50 pmol/L for the first trimester, and 11.22-18.19 pmol/L and 3.60-5.41 pmol/L for the second trimester, and 10.19-17.42 pmol/L and 3.37-4.79 pmol/L for the third trimester, respectively (both p < 0.001). CONCLUSION: It is necessary to establish assay method- and trimester-specific reference intervals for thyroid-stimulating hormone, free thyroxine, and free triiodothyronine because the reference intervals of these thyroid hormones are significantly different at different stages of pregnancy.

Hyperhomocysteinemia as a metabolic disorder parameter is independently associated with the severity of coronary heart disease.

OBJECTIVES: To study the associations between hyperhomocysteinemia (HHcy) and the severity of coronary heart disease (CHD). METHODS: We retrospectively analyzed metabolic parameters, anthropometric variables, and life style habits in 292 CHD patients of different categories, and 100 controlled non-CHD patients with chest pain symptoms who were hospitalized in the Department of Cardiovascular Medicine, Sichuan Academy of Medical Sciences and Sichuan Provincial People's Hospital, Chengdu, China between October 2013 and September 2014. RESULTS: The prevalence of HHcy in CHD patients was 79.1%, while only 5% of non-CHD patients had elevated serum homocysteine (Hcy) concentrations. The prevalence of HHcy significantly increased from 5% in non-CHD controls to 66% in the stable angina pectoris (SAP) group, to 81.9% in the unstable angina pectoris group, and to 93.15% in the acute myocardial infarction (AMI) group (p less than 0.001). After adjusting for confounding factors, multivariate logistic regression analysis showed that HHcy was independently associated with CHD category (AMI versus SAP, odds ratio [6.38], 95% confidence interval; 1.18-34.46). The Hcy was negatively correlated with folic acid (r=-0.67, p less than 0.001) and vitamin B12 (r=-0.56, p less than 0.001). Of the CHD patients with HHcy, 51.1% had low folic acid and 42% had low vitamin B12, 7 or 5 times higher than that of CHD patients with normal-low Hcy concentrations (p less than 0.001). CONCLUSION: Hyperhomocysteinemia is independently associated with the severity of CHD, and significantly correlated with low status of folic acid and vitamin B12 in CHD patients.