title: Newborn screening for congenital hypothyroidism in very-low-birth-weight babies: the need for a second test.
abstract: BACKGROUND
  Very-low-birth-weight babies (VLBW) with hypothyroidism may show a delayed postnatal rise in thyroid stimulating hormone (TSH), mainly due to immaturity of the hypothalamic-pituitary-thyroid axis. Transient hypothyroidism is prevalent in VLBW babies and some affected babies are considered to need treatment. There is disagreement about whether a second screening test is needed in VLBW babies to detect all cases that need treatment.
  
  
  METHODS
  We included in the study all babies with a birth weight ≤ 1,500 g born in New South Wales and the Australian Capital Territory between January 2006 and December 2008. Newborn screening samples for TSH measurement were taken in the first days of life and again at 1 month. During week 1, a blood-spot TSH level of  ≥20 mIU/L was considered positive, and at 1 month a positive level was  ≥7 mIU/L, and triggered full investigation.
  
  
  RESULTS
  In the cohort of 301,000 babies, 2,313 VLBW babies survived for testing, and 2,117 repeat screening samples were received. Forty-three babies had transient hypothyroidism, with thyroid function normalising before 2 months of age, usually without treatment. Eighteen babies required treatment beyond 2 months of age (1:128 of surviving babies), 16 having had normal TSH results on initial testing, and 12 having levels below 6 mIU/L.
  
  
  CONCLUSIONS
  Significant hypothyroidism, transient or permanent, but persisting beyond 2 months of age is common in VLBW babies. There is a delayed rise in TSH in some, and secondary screening at 1 month of age detects babies deemed by local paediatric endocrinologists as needing treatment.
authors.affiliation: The Children's Hospital at Westmead, Westmead, NSW, Australia. bijarnia@gmail.com
authors.forename: Sunita
authors.initials: S
authors.lastname: Bijarnia
authors.forename: Bridget
authors.initials: B
authors.lastname: Wilcken
authors.forename: Veronica C
authors.initials: VC
authors.lastname: Wiley
mesh_terms: D001800:Blood Specimen Collection / Q000379:methods; D003409:Congenital Hypothyroidism / Q000175:diagnosis*; D005260:Female; D005865:Gestational Age; D006301:Health Services Needs and Demand; D006801:Humans; D007231:Infant, Newborn; D007232:Infant, Newborn, Diseases / Q000097:blood / Q000175:diagnosis; D019102:Infant, Very Low Birth Weight / Q000097:blood; D008297:Male; D015997:Neonatal Screening / Q000379:methods*; D013960:Thyroid Function Tests / Q000379:methods*; D013972:Thyrotropin / Q000032:analysis / Q000097:blood
chemical_list: D013972:Thyrotropin