title: The Urine Iodine to Creatinine as an Optimal Index of Iodine During Pregnancy in an Iodine Adequate Area in China.
abstract: BACKGROUND
  Iodine nutrition is a global event, especially for pregnant women.
  
  
  OBJECTIVE
  To develop applicable index of iodine intake for population during pregnancy.
  
  
  METHODS
  From 2012 to 2014, pregnant women at less than 8 weeks of gestation (n = 222) and reproductive-age women (n = 827) participated in this study. The pregnant women were evaluated at follow-up visits at 8, 12, 16, 20, 28, and 36 weeks of gestation and 3 and 6 months postpartum.
  
  
  METHODS
  Twenty-four-hour urine samples were collected at weeks 8 of gestation. Urine iodine (UI) and creatinine (Cr) and serum thyroglobulin were measured in all of the subjects. Circulatory iodine was measured using inductively coupled plasma-mass spectrometry at 8, 20, and 36 weeks of gestation and 6 months postpartum.
  
  
  RESULTS
  The median UI concentration decreased from 183.6 to 104.2 μg/L during pregnancy. The serum iodine (SI) changes were similar to the UI to creatinine ratio (UI/Cr). The SI level was lowest at the eighth week of gestation (60.5 μg/L), which rose significantly until 20 weeks (106.5 μg/L) and then began to decline (36 wk, 84.7 μg/L). The 24-hour UI excretion measurement was regarded as the gold standard. The area under the receiver-operating characteristic curve for UI/Cr was 0.92 for iodine deficiency diagnoses and 0.78 for SI. The area for SI was 0.82 for excessive iodine diagnoses and 0.75 for UI/Cr. The areas under these curves were significantly different (P < .001). The areas under the receiver-operating characteristic curve for UI were 0.61 (P = .11) and 0.65 (P = .08) for iodine deficiency and excessive iodine diagnoses, respectively. Additionally, for thyroglobulin, these values were 0.54 (P = .53) and 0.53 (P = .74), respectively.
  
  
  CONCLUSIONS
  Iodine intake, as assessed by spot UI concentration in pregnant women, is inaccurate and increases the prevalence of iodine deficiency. The UI/Cr better reflects the 24-hour iodine excretion and circulating iodine levels during pregnancy and the postpartum period.
authors.affiliation: Endocrine Institute and Liaoning Provincial Key Laboratory of Endocrine Diseases (C.L., S.P., X.X., J.M., X.T., Z.S., W.T.), Department of Endocrinology and Metabolism, First Hospital of China Medical University, 110001 Shenyang, China; and Department of Endocrinology (X.Z., D.W.), First Hospital of Dandong, 118000 Dandong, China.
authors.forename: Chenyan
authors.initials: C
authors.lastname: Li
authors.affiliation: Endocrine Institute and Liaoning Provincial Key Laboratory of Endocrine Diseases (C.L., S.P., X.X., J.M., X.T., Z.S., W.T.), Department of Endocrinology and Metabolism, First Hospital of China Medical University, 110001 Shenyang, China; and Department of Endocrinology (X.Z., D.W.), First Hospital of Dandong, 118000 Dandong, China.
authors.forename: Shiqiao
authors.initials: S
authors.lastname: Peng
authors.affiliation: Endocrine Institute and Liaoning Provincial Key Laboratory of Endocrine Diseases (C.L., S.P., X.X., J.M., X.T., Z.S., W.T.), Department of Endocrinology and Metabolism, First Hospital of China Medical University, 110001 Shenyang, China; and Department of Endocrinology (X.Z., D.W.), First Hospital of Dandong, 118000 Dandong, China.
authors.forename: Xiaomei
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Endocrine Institute and Liaoning Provincial Key Laboratory of Endocrine Diseases (C.L., S.P., X.X., J.M., X.T., Z.S., W.T.), Department of Endocrinology and Metabolism, First Hospital of China Medical University, 110001 Shenyang, China; and Department of Endocrinology (X.Z., D.W.), First Hospital of Dandong, 118000 Dandong, China.
authors.forename: Xiaochen
authors.initials: X
authors.lastname: Xie
authors.affiliation: Endocrine Institute and Liaoning Provincial Key Laboratory of Endocrine Diseases (C.L., S.P., X.X., J.M., X.T., Z.S., W.T.), Department of Endocrinology and Metabolism, First Hospital of China Medical University, 110001 Shenyang, China; and Department of Endocrinology (X.Z., D.W.), First Hospital of Dandong, 118000 Dandong, China.
authors.forename: Danyang
authors.initials: D
authors.lastname: Wang
authors.affiliation: Endocrine Institute and Liaoning Provincial Key Laboratory of Endocrine Diseases (C.L., S.P., X.X., J.M., X.T., Z.S., W.T.), Department of Endocrinology and Metabolism, First Hospital of China Medical University, 110001 Shenyang, China; and Department of Endocrinology (X.Z., D.W.), First Hospital of Dandong, 118000 Dandong, China.
authors.forename: Jinyuan
authors.initials: J
authors.lastname: Mao
authors.affiliation: Endocrine Institute and Liaoning Provincial Key Laboratory of Endocrine Diseases (C.L., S.P., X.X., J.M., X.T., Z.S., W.T.), Department of Endocrinology and Metabolism, First Hospital of China Medical University, 110001 Shenyang, China; and Department of Endocrinology (X.Z., D.W.), First Hospital of Dandong, 118000 Dandong, China.
authors.forename: Xiaochun
authors.initials: X
authors.lastname: Teng
authors.affiliation: Endocrine Institute and Liaoning Provincial Key Laboratory of Endocrine Diseases (C.L., S.P., X.X., J.M., X.T., Z.S., W.T.), Department of Endocrinology and Metabolism, First Hospital of China Medical University, 110001 Shenyang, China; and Department of Endocrinology (X.Z., D.W.), First Hospital of Dandong, 118000 Dandong, China.
authors.forename: Zhongyan
authors.initials: Z
authors.lastname: Shan
authors.affiliation: Endocrine Institute and Liaoning Provincial Key Laboratory of Endocrine Diseases (C.L., S.P., X.X., J.M., X.T., Z.S., W.T.), Department of Endocrinology and Metabolism, First Hospital of China Medical University, 110001 Shenyang, China; and Department of Endocrinology (X.Z., D.W.), First Hospital of Dandong, 118000 Dandong, China.
authors.forename: Weiping
authors.initials: W
authors.lastname: Teng
mesh_terms: D000328:Adult; D002138:Calibration; D002681:China / Q000453:epidemiology; D003404:Creatinine / Q000652:urine*; D005260:Female; D006305:Health Status Indicators; D006801:Humans; D007037:Hypothyroidism / Q000175:diagnosis* / Q000453:epidemiology / Q000652:urine; D007455:Iodine / Q000172:deficiency / Q000652:urine*; D009752:Nutritional Status; D011247:Pregnancy; D011248:Pregnancy Complications / Q000175:diagnosis* / Q000453:epidemiology / Q000652:urine; D011296:Prenatal Diagnosis / Q000379:methods / Q000592:standards*; D013954:Thyroglobulin / Q000097:blood; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood; D055815:Young Adult
chemical_list: D013972:Thyrotropin; D013954:Thyroglobulin; D007455:Iodine; D003404:Creatinine; D013974:Thyroxine