| Part1Study on the prevalence of thyroid diseases during different trimesters of pregnancy in excess and sufficient iodine areain Jiangsu ProvinceBackground Thyroid disorders are common in pregnant women. Pregnancy can interfere the course of thyroid disease, while uncontrolled thyroid disorders can result in adverse obstetric outcomes. Thyroid hormone is crucial to the development of fetus central nervous system, insufficient thyroid function during pregnancy will not only adversely affect pregnancy outcome, damage the fetal neurological development, but also increase the incidence of metabolic disorders in their offspring.Aim To investigate the prevalence of thyroid disorders during different trimesters of pregnancy in both excess and sufficient iodine areas in Jiangsu Province.Objectives We selected396women aged17-40years who went to obstetric clinics in excess and sufficient iodine region for early pregnancy consultation.Method Questionnaires were completed to record general information of the pregnant women. Physical examinations were performed and blood samples were collected for thyroid function and autoantibody detection. Baseline data and results of the checkups were input in Epidata and analyzed by STATA10.0.Result There was no difference between the age, body weight, prevalence of hypertension and vomiting. Serum FT3, FT4and TT4of women in excess iodine area were significantly lower than those of sufficient iodine area, while TSH remarkably higher. Serum TT4showed significantly lower in the second trimester in excess iodine region. Both FT3and FT4in the two places decreased with the gestational age. The overall prevalence of thyroid disorders throughout pregnancy in both places was62.44%, which was obviously higher in excess iodine region (67.45%vs46.88%). All kinds of thyroid dysfunction revealed no difference in prevelance between the two regions in the first and second trimesters. The incidence of hypothyroidism in the third trimester in much higher in sufficient iodine region. We established pregnancy specific reference of thyroid function in excess iodine region in Jiangsu Province, FT33.29-5.99pmol/L, FT414.09-21.62pmol/L, TT468.97-197.03nmol/L, TSH0.12-2.40μIU/ml. The diagnostic criteria of thyroid disease for general population presented with low sensitivity in diagnosing hypothyroidism, subclinical hypothyroidism and hypothyroxinemia in pregnancy, especialy in the first trimester. It also showed low sensitivity when using TT4to confirm hypothyroxinemia instead of FT4.Conclusion The overall prevalence of thyroid dysfunction is significantly higher in excess iodine region. Thyroid diseases were more common in the first trimester in excess iodine area than in sufficient iodine area, but without significance. A great part of pregnant women with thyroid dysfunction would be missed if the diagnosis is made according to the reference of general population, especially in the first trimester. The diagnostic efficacy is lower in confirming hypothyroxinemia with TT4instead of FT4. We recommend using pregnancy specific reference. Part2Study on trimester-specific reference ranges for thyroid hormones in pregnant women in NanjingObjective To determine the trimester-specific reference range of thyroid function in Nanjing.Methods A prospective, observational study was undertaken to learn the trimester-specific reference range in Nanjing. Pregnant women were recruited when they came to routine antenatal clinic. There were288,255,262pregnant women of first, second and third trimester enrolled respectively, while another282subjects without pregnancy were selected as control. After signing informed consent form, a questionnaire was completed by the subjects to record their personal health history, family history of thyroid disease, and consumption of estrogen or antithyroid drugs. Thyroid palpation was performed to exclude thyroid goiter. Thyroid function (TSH, FT3, FT4, TT3, TT4, TPO-Ab) and urine iodine were measured by Chemiluminescence and arsenic cerium catalysis.Results The trimester-specific reference range in Nanjing were as follows, TSH:0.02-3.78mIU/1, FT4:13.93-26.49pmol/1, TT4:103.39-319.43nmol/1in first trimester. TSH:0.47-3.89mIU/1, FT4:12.33-19.33pmol/1, TT4:92.28-234.88nmol/1in second trimester. TSH:0.55-4.91mIU/1, FT4:11.38-19.21pmol/1, TT4:83.54-258.12nmol/1in third trimester. According to the TSH reference range recommended by ATA, the prevalence of subclinical hypothyroidism, hypothyroidism, subclinical hyperthyroidism, hyperthyroidism, hypothyroxinemia and TPOAb positive were12.42%,0.50%,0.99%,0.99%,1.61%,11.80%, respectively. It turned out to be1.99%,0.25%,1.61%,0.37%,1.61%when trimester-specific reference range was refered to, which showed elevation of hypothyroxinemia incidence and decline rate of subclinical hypothyroidism and hyperthyroidism.Cnclusions Trimester-specific reference range is different from the one recommended by ATA, which might have an influence on the diagnosis and treatment of thyroid dysfunction during pregnancy. So it is essential for clinical labs to set up their own trimester-specific reference in different iodine areas.
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