title: Subclinical hyperthyroidism and pregnancy outcomes.
abstract: OBJECTIVE
  Subclinical hyperthyroidism has long-term sequelae that include osteoporosis, cardiovascular morbidity, and progression to overt thyrotoxicosis or thyroid failure. The objective of this study was to evaluate pregnancy outcomes in women with suppressed thyroid-stimulating hormone (TSH) and normal free thyroxine (fT(4)) levels.
  
  
  METHODS
  All women who presented to Parkland Hospital for prenatal care between November 1, 2000, and April 14, 2003, underwent thyroid screening by chemiluminescent TSH assay. Women with TSH values at or below the 2.5th percentile for gestational age and whose serum fT(4) levels were 1.75 ng/dL or less were identified to have subclinical hyperthyroidism. Those women screened and delivered of a singleton infant weighing 500 g or more were analyzed. Pregnancy outcomes in women identified with subclinical hyperthyroidism were compared with those in women whose TSH values were between the 5th and 95th percentiles.
  
  
  RESULTS
  A total of 25,765 women underwent thyroid screening and were delivered of singleton infants. Of these, 433 (1.7%) were considered to have subclinical hyperthyroidism, which occurred more frequently in African-American and/or parous women. Pregnancies in women with subclinical hyperthyroidism were less likely to be complicated by hypertension (adjusted odds ratio 0.66, 95% confidence interval 0.44-0.98). All other pregnancy complications and perinatal morbidity or mortality were not increased in women with subclinical hyperthyroidism.
  
  
  CONCLUSIONS
  Subclinical hyperthyroidism is not associated with adverse pregnancy outcomes. Our results indicate that identification of subclinical hyperthyroidism and treatment during pregnancy is unwarranted.
  
  
  METHODS
  II-2.
authors.affiliation: Department of Obstetrics and Gynecology, the University of Texas Southwestern Medical Center, Dallas, 75390, USA. brian.casey@utsouthwestern.edu
authors.forename: Brian M
authors.initials: BM
authors.lastname: Casey
authors.forename: Jodi S
authors.initials: JS
authors.lastname: Dashe
authors.forename: C Edward
authors.initials: CE
authors.lastname: Wells
authors.forename: Donald D
authors.initials: DD
authors.lastname: McIntire
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Leveno
authors.forename: F Gary
authors.initials: FG
authors.lastname: Cunningham
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D006980:Hyperthyroidism / Q000097:blood / Q000453:epidemiology; D011247:Pregnancy; D011248:Pregnancy Complications / Q000097:blood / Q000453:epidemiology; D011256:Pregnancy Outcome; D015995:Prevalence; D013972:Thyrotropin / Q000097:blood
chemical_list: D013972:Thyrotropin