title: High prevalence of thyroid disorders in pregnant women in a mildly iodine-deficient country: a population-based study.
abstract: BACKGROUND
  Many countries in Europe remain mildly iodine deficient but relatively few country-level data exist on mild iodine deficiency (MID) and its impact on thyroid function in pregnant women.
  
  
  OBJECTIVE
  To determine the prevalence of thyroid disorders in pregnant women in Belgium and to assess the association between iodine status and serum thyroglobulin (Tg).
  
  
  METHODS
  We conducted a national survey of pregnant women in 55 obstetric clinics. Urinary iodine concentration corrected for creatinine (UIC/Cr) and thyroid function were measured.
  
  
  RESULTS
  The frequency of elevated serum TSH was 7.2%, indicating either subclinical hypothyroidism (6.8%) or overt hypothyroidism (0.4%). Among those women, 13.8% were thyroid peroxidase antibodies (TPO-Ab) positive. The frequency of low serum TSH was 4.1%, indicating either subclinical hyperthyroidism (3.6%) or overt hyperthyroidism (0.5%). In the entire population, the frequency of positive TPO-Ab and/or Tg antibodies positive women was 4%. Globally, the prevalence of thyroid disorders (abnormally high or low TSH) or thyroid autoimmunity features was 15.3% and 18.6% in first-trimester pregnant women. Women with an adequate iodine status (UIC/Cr = 150-249 μg/g) had a significantly lower median Tg concentration compared to moderately iodine deficient women (UIC/Cr ≤ 49 μg/g), 19 μg/L and 25 μg/L, respectively.
  
  
  CONCLUSIONS
  The prevalence of thyroid disorders was high, affecting one in six pregnant women in Belgium. Therefore, the iodine status in women needs to be improved and screening for thyroid disease should be performed early in pregnancy. In addition, our data suggest that a median Tg of <20 μg/L may indicate iodine sufficiency in pregnant women.
authors.affiliation: Department of Nuclear Medicine, Hôpital Erasme, Université Libre de Bruxelles, Route de Lennik 808, 1070 Brussels, Belgium. rmorenor@ulb.ac.be
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Moreno-Reyes
authors.forename: Daniel
authors.initials: D
authors.lastname: Glinoer
authors.forename: Herman
authors.initials: H
authors.lastname: Van Oyen
authors.forename: Stefanie
authors.initials: S
authors.lastname: Vandevijvere
mesh_terms: D000328:Adult; D001323:Autoantibodies / Q000097:blood; D001530:Belgium / Q000453:epidemiology; D005260:Female; D006306:Health Surveys; D006801:Humans; D007455:Iodine / Q000172:deficiency* / Q000652:urine; D011247:Pregnancy; D011248:Pregnancy Complications / Q000097:blood / Q000175:diagnosis / Q000453:epidemiology*; D015995:Prevalence; D013954:Thyroglobulin / Q000097:blood; D013959:Thyroid Diseases / Q000097:blood / Q000175:diagnosis / Q000453:epidemiology*; D013960:Thyroid Function Tests; D013963:Thyroid Hormones / Q000097:blood*
chemical_list: D001323:Autoantibodies; D013963:Thyroid Hormones; D013954:Thyroglobulin; D007455:Iodine