title: Establishing trimester-specific maternal thyroid function reference intervals.
abstract: BACKGROUND
  Thyroid disorders are common in women of childbearing age and are associated with adverse pregnancy outcomes. Physiological changes in pregnancy and the lack of pregnancy-specific reference ranges make managing thyroid disorders in pregnancy challenging. Our aim was to establish trimester-specific thyroid function reference intervals throughout pregnancy, and to examine the prevalence of thyroid autoimmunity in otherwise euthyroid women.
  
  
  METHODS
  This was a prospective, cross-sectional study of thyroid function tests (TFTs) in pregnant women attending a large, tertiary referral maternity hospital. Patients with known thyroid disorders, autoimmune disease, recurrent miscarriage, hyperemesis gravidarum and pre-eclampsia were excluded. TFTs were analysed in the CUH biochemistry laboratory using Roche Modular E170 electrochemiluminescent immunoassay. Trimester-specific reference ranges (2.5th, 50th and 97.5th centiles) were calculated.
  
  
  RESULTS
  Three-hundred-and-fifty-one women were included into the analysis. Median maternal age was 30. Thyroid-stimulating hormone concentrations showed slightly increasing median centile throughout gestation. Free thyroxine (T4) and T3 decreased throughout gestation. Table 1 demonstrates the calculated percentiles according to gestational weeks.
  
  
  CONCLUSIONS
  We established pregnancy-specific thyroid function reference intervals for our pregnant population, for use in clinical practice.
authors.affiliation: Anu Research Centre, Department of Obstetrics and Gynaecology, University College Cork, Cork University Maternity Hospital, Cork, Republic of Ireland.
authors.forename: Azy S
authors.initials: AS
authors.lastname: Khalid
authors.forename: Zbigniew
authors.initials: Z
authors.lastname: Marchocki
authors.forename: Kevin
authors.initials: K
authors.lastname: Hayes
authors.forename: Jennifer E
authors.initials: JE
authors.lastname: Lutomski
authors.forename: Caroline
authors.initials: C
authors.lastname: Joyce
authors.forename: Mary
authors.initials: M
authors.lastname: Stapleton
authors.forename: John
authors.initials: J
authors.lastname: O'Mullane
authors.forename: Keelin
authors.initials: K
authors.lastname: O'Donoghue
mesh_terms: D000328:Adult; D015551:Autoimmunity; D005260:Female; D006801:Humans; D009035:Mothers; D011247:Pregnancy; D011264:Pregnancy Trimesters / Q000097:blood / Q000276:immunology / Q000502:physiology*; D012016:Reference Values; D012306:Risk; D013960:Thyroid Function Tests / Q000592:standards*; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
chemical_list: D014284:Triiodothyronine; D013972:Thyrotropin; D013974:Thyroxine
keywords: Thyroid hormones; analytes; clinical studies; immunoassay; pregnancy