title: [The changes of thyrotropin level in euthyroid population: a 5-year follow-up study in communities with different iodine intakes].
abstract: OBJECTIVE
  To determine the factors that influence the development of abnormal thyrotropin (TSH) level in an euthyroid population.
  
  
  METHODS
  We conducted a follow-up study in 3 communities with different iodine status. Of the 3403 euthyroid subjects at baseline screened in 1999, 80.1% (n = 2727) was visited and sampled in 2004 for measuring TSH, thyroid peroxidase antibody (TPOAb) and thyroglobulin antibody (TgAb).
  
  
  RESULTS
  Iodine status in the 3 communities were stable. Decreased TSH level (< 0.3 mU/L) developed in 2.5% (n = 68) of sampled subjects, while raised TSH level (> 4.8 mU/L) in 2.4% (n = 64). A logistic analysis showed that risk factors for developing decreased TSH level included positive conversion of TPOAb (OR = 5.5), positive TPOAb both in 1999 and in 2004 (OR = 4.0), positive TgAb in 2004 (OR = 3.7) and TSH < 1.0 mU/L in 1999 (OR = 2.6). Risk factors involved in developing raised TSH level included iodine status of Zhangwu community (OR = 4.1), iodine status of Huanghua community (OR = 3.9), positive TgAb in 2004 (OR = 3.7), positive TPOAb both in 1999 and 2004 (OR = 3.6), positive conversion of TPOAb (OR = 2.7) and TSH > 1.9 mU/L in 1999 (OR = 2.6).
  
  
  CONCLUSIONS
  Exposure to long-term iodine excess imposes danger of developing hypothyroidism. The risk will be even higher when exposing to iodine adequacy after correction of iodine deficiency. An interval between 1.0 and 1.9 mU/L of TSH level was optimal with the least probability of developing abnormal TSH level.
authors: Department of Endocrinology and Metabolism, Institute of Endocrinology, The First Affiliated Hospital of China Medical University, Shenyang 110001, China.
authors: Hai-Xia
authors: HX
authors: Guan
authors: Yan-Yan
authors: YY
authors: Chen
authors: Zhong-Yan
authors: ZY
authors: Shan
authors: Xiao-Chun
authors: XC
authors: Teng
authors: Di
authors: D
authors: Teng
authors: Yu-Shu
authors: YS
authors: Li
authors: Xiao-Hui
authors: XH
authors: Yu
authors: Chen-Ling
authors: CL
authors: Fan
authors: Wei
authors: W
authors: Chong
authors: Fan
authors: F
authors: Yang
authors: Hong
authors: H
authors: Dai
authors: Yang
authors: Y
authors: Yu
authors: Jia
authors: J
authors: Li
authors: Dong
authors: D
authors: Zhao
authors: Jin-Yuan
authors: JY
authors: Mao
authors: Wei-Ping
authors: WP
authors: Teng
mesh_terms: D000328:Adult; D001323:Autoantibodies / Q000097:blood; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007455:Iodine / Q000008:administration & dosage*; D008297:Male; D008875:Middle Aged; D009752:Nutritional Status; D013959:Thyroid Diseases / Q000517:prevention & control*; D013961:Thyroid Gland / Q000502:physiology; D013972:Thyrotropin / Q000097:blood*
chemical_list: D001323:Autoantibodies; C006606:anti-thyroglobulin; C056626:thyroid microsomal antibodies; D013972:Thyrotropin; D007455:Iodine