UMEM Educational Pearls

Title: Congenital Hypothyroidism - Don't Street Until You Treat

Keywords: Newborn screen, pediatrics, hypothyroidism, neonatal, congenital (PubMed Search)

Posted: 3/18/2010 by Adam Friedlander, MD (Updated: 3/20/2010)
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Congenital hypothyroidism (CH) is almost uniformly identified before symptoms develop because of newborn screening. Though this problem will rarely present to the Emergency Department, it is not uncommon for parents with poor access to care to present to EDs after being notified of an abnormal screen. Here is what you need to know:

CH affects 1 / 3,000 live births
When left untreated, there are many sequelae, but the most important by far is almost certain profound mental retardation
Children treated within two weeks of birth have NORMAL intellect when followed into adolescence (compared to sibs, age matched controls)
Children treated after two weeks have measurable declines in cognitive ability and motor skills - even though they may not develop MR, they are at VERY HIGH risk

So:

Start treatment on ALL infants you encounter with CH, IMMEDIATELY if they are approaching 14 days of age
Consider admission if there is any chance of a parent having poor access to prescription coverage or close followup
Goal levels of T4 are >10 mcg/dL; infants with very low levels need IMMEDIATE TREATMENT with high dose-range levothyroxine - any delay can lead to drops of up to 20 IQ points
Initial dose of Levothyroxine is at least 10-15 mcg/kg/day
Tablets must be crushed and mixed with breast milk or formula, and NOT with soy, calcium or iron-containing substances which decrease levothyroxine absorption. Liquid preparations are unreliable.

References

Selva KA; Harper A; Downs A; Blasco PA; Lafranchi SH, Neurodevelopmental outcomes in congenital hypothyroidism: comparison of initial T4 dose and time to reach target T4 and TSH. J Pediatr. 2005 Dec;147(6):775-80.
LaFranchi SH; Austin J, How should we be treating children with congenital hypothyroidism?. J Pediatr Endocrinol Metab. 2007 May;20(5):559-78.
Germak, JA, Foley, TP Jr., Longitudinal assessment of L-thyroxine therapy for congenital hypothyroidism. J Pediatr 1990; 117:211.
Bongers-Schokking, JJ, de Muinck, Keizer-Schrama, SM. Influence of timing and dose of thyroid hormone replacement on mental, psychomotor, and behavioral development in children with congenital hypothyroidism. J Pediatr 2005; 147:768.