Different Doses of Levothyroxine Provide Similar Outcomes in Infants With Congenital Hypothyroidism: Presented at ESPE

By Chris Berrie

BARCELONA, Spain -- October 6, 2015 -- Different initial doses of levothyroxine provide similar outcomes in growth and neurocognitive development during the first year of life in infants with congenital hypothyroidism, according to a study presented here on October 3 at the 54th Annual Meeting of the European Society for Paediatric Endocrinology (ESPE).

The recommended initial levothyroxine dose in newborns with congenital hypothyroidism is 10 to 15 mcg/kg/day. While starting on a higher dose can lead to early achievement of euthyroid status and better full-scale intelligence quotient scores, higher doses may also result in neurodevelopmental and behavioural problems and lower verbal scores.

“We wondered if it is possible to identify a better [levothyroxine] initial dose to reach optimal neurocognitive outcomes,” explained Andrea Esposito, MD, Paediatric Endocrine Unit, ‘Federico II’ University of Naples, Naples, Italy.

The researchers evaluated the effects of levothyroxine 10.0 to 12.5 mcg/kg/day (n = 33) and levothyroxine 12.6 to 15.0 mcg/kg/day (n = 35). The doses were modified within these ranges to maintain serum thyroid-stimulating hormone (TSH) between 0.5 and 2.0 mU/L, and serum free thyroxine in the upper normal range (0.9-1.7 ng/dL).

Over the first 12 months of their lives, the infants showed no significant differences in thyroid function, as determined by TSH levels and free thyroxine. There were also no significant differences in growth (length SDS and weight SDS) or cognitive development, which was evaluated with Griffiths mental development scales.

However, “8 patients [11%] showed a sub-optimal total IQ development of below 90,” noted Dr. Esposito.

Factors associated with an IQ of <90 versus >90 included age at diagnosis (P< .05) and Graffar’s socioeconomic score (16.00 vs. 12.65; P < .05) appeared to be risk factors.

“Long-term follow-up of these children will better clarify the influence of different levothyroxine starting doses on neurocognitive outcomes, and the influence and role of other prognostic factors,” said Dr. Esposito.

[Presentation title: Effects of Initial Levothyroxine Dose on Growth and Neurodevelopment Outcomes During the First Year of Life in Children With Congenital Hypothyroidism. Abstract FC13.4]

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