title: Maternal thyroid function at 11-13 weeks of gestation in fetal trisomies 21 and 18.
abstract: OBJECTIVE
  To examine the association between maternal serum levels of thyroid stimulating hormone (TSH) and free β-human chorionic gonadotrophin (free β-hCG) in trisomy 21, trisomy 18 and euploid pregnancies at 11-13 weeks and investigate the potential value of TSH in first-trimester screening for aneuploidies.
  
  
  METHODS
  Maternal serum TSH and free β-hCG levels at 11-13 weeks in 25 trisomy 21 and 25 trisomy 18 pregnancies were compared with levels in 3592 unaffected pregnancies. Only women with no history of thyroid disease and negative for antithyroid antibodies were included.
  
  
  RESULTS
  Serum TSH in the trisomy 21 pregnancies was lower [0.76 multiples of the normal median (MoM), interquartile range (IQR) 0.46-1.09 MoM] and in trisomy 18 it was higher (1.25 MoM, IQR 0.88-1.98 MoM) than in unaffected pregnancies (1.01 MoM, IQR 0.61-1.51 MoM). There were significant associations between TSH and free β-hCG in the unaffected pregnancies (r = - 0.214, p < 0.0001), but not in those with trisomy 21 (r = - 0.157, p = 0.452) or trisomy 18 (r = - 0.176, p = 0.401).
  
  
  CONCLUSIONS
  hCG, rather than TSH, may be the primary thyrotropic factor in early pregnancy. Measurement of TSH does not improve the performance of screening for trisomies 21 and 18 provided by nuchal translucency, free β-hCG and pregnancy-associated plasma protein-A.
authors.affiliation: Harris Birthright Research Centre for Fetal Medicine, King's College Hospital, London, UK.
authors.forename: Ghalia
authors.initials: G
authors.lastname: Ashoor
authors.forename: Nerea
authors.initials: N
authors.lastname: Maiz
authors.forename: Howard
authors.initials: H
authors.lastname: Cuckle
authors.forename: Firas
authors.initials: F
authors.lastname: Jawdat
authors.forename: Kypros H
authors.initials: KH
authors.lastname: Nicolaides
mesh_terms: D000328:Adult; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000097:blood; D002887:Chromosomes, Human, Pair 18 / Q000235:genetics*; D004314:Down Syndrome / Q000097:blood* / Q000000981:diagnostic imaging; D005260:Female; D005865:Gestational Age; D006801:Humans; D008423:Maternal Age; D048208:Nuchal Translucency Measurement; D011247:Pregnancy; D011266:Pregnancy-Associated Plasma Protein-A / Q000032:analysis; D011296:Prenatal Diagnosis / Q000379:methods*; D012189:Retrospective Studies; D013961:Thyroid Gland / Q000503:physiopathology*; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood; D057885:Triploidy; D014314:Trisomy
chemical_list: D018997:Chorionic Gonadotropin, beta Subunit, Human; D014284:Triiodothyronine; D013972:Thyrotropin; D011266:Pregnancy-Associated Plasma Protein-A; D013974:Thyroxine