Pitfalls in Screening Programs for Congenital Hypothyroidism in Premature Newborns

ABSTRACT

Sick premature infants may display transient hypothyroxinemia secondary to immaturity of the hypothalamic-pituitary axis. Therefore, early screening programs of such infants may be misleading. We present such a case report, with review of the literature and the following suggested recommendations. (1) Screening programs should report thyroid-stimulating hormone (TSH) as well as thyroxine (T₄) levels in premature infants, which will allow the treating physicians to be aware of possible abnormality that needs to be followed. (2) Sick premature infants and other populations at risk should undergo a full serum thyroid function evaluation including free T₄ and TSH beyond the screening program at discharge or at 30 days of age, whichever comes first. (3) Physicians should use their clinical judgment and experience even in the face of normal newborn thyroid screening test and reevaluate for hypothyroidism when there is a clinical suspicion. Our case report is a reminder of the American Academy of Pediatrics guidelines with practical suggestions for extra caution to avoid missing primary hypothyroidism in sick premature infants.

KEYWORDS

Congenital hypothyroidism - preterm infants - screening program

REFERENCES

• 1 American Academy of Pediatrics, Rose SR and the Section on Endocrinology and the Committee on Genetics, American Thyroid Association, Brown RS and the Public Health Committee, Lawson Wilkins Pediatric Endocrine Society . Update of newborn screening and therapy for congenital hypothyroidism.  Pediatrics. 2006;  117 2290-2303
• 2 Forghani N, Aye T. Hypothroxinemia and prematurity.  NeoReviews. 2008;  9 e66-e71
• 3 Fisher D A. Hypothyroxinemia in premature infants: is thyroxine treatment necessary?.  Thyroid. 1999;  9 715-720
• 4 Reuss M L, Paneth N, Pinto-Martin J A, Lorenz J M, Susser M. The relation of transient hypothyroxinemia in preterm infants to neurologic development at two years of age.  N Engl J Med. 1996;  334 821-827
• 5 Paul D A, Leef K H, Stefano J L, Bartoshesky L. Low serum thyroxine on initial newborn screening is associated with intraventricular hemorrhage and death in very low birth weight infants.  Pediatrics. 1998;  101 903-907
• 6 van Wassenaer A G, Kok J H, de Vijlder J J et al.. Effects of thyroxine supplementation on neurologic development in infants born at less than 30 weeks' gestation.  N Engl J Med. 1997;  336 21-26
• 7 van Wassenaer A G, Westera J, Houtzager B A, Kok J H. Ten-year follow-up of children born at < 30 weeks' gestational age supplemented with thyroxine in the neonatal period in a randomized, controlled trial.  Pediatrics. 2005;  116 e613-e618
• 8 Osborn D A, Hunt R W. Prophylactic postnatal thyroid hormones for prevention of morbidity and mortality in preterm infants.  Cochrane Database Syst Rev. 2007;  CD005948
• 9 Moreno J C, Klootwijk W, van Toor H et al.. Mutations in the iodotyrosine deiodinase gene and hypothyroidism.  N Engl J Med. 2008;  358 1811-1818
• 10 Holtzman C, Slazyk W E, Cordero J F, Hannon W H. Descriptive epidemiology of missed cases of phenylketonuria and congenital hypothyroidism.  Pediatrics. 1986;  78 553-558
• 11 Korada M, Pearce M S, Ward Platt M P et al.. Repeat testing for congenital hypothyroidism in preterm infants is unnecessary with an appropriate thyroid stimulating hormone threshold.  Arch Dis Child Fetal Neonatal Ed. 2008;  93 F286-288
• 12 Larson C, Hermos R, Delaney A, Daley D, Mitchell M. Risk factors associated with delayed thyrotropin elevations in congenital hypothyroidism.  J Pediatr. 2003;  143 587-591