Mean high dose L-thyroxine treatment is efficient and safe to achieve a normal IQ in young adult patients with congenital hypothyroidism.

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Mean high dose L-thyroxine treatment is efficient and safe to achieve a normal IQ in young adult patients with congenital hypothyroidism.

J Clin Endocrinol Metab. 2018 Jan 09;:

Authors: Aleksander P, Brückner-Spieler M, Stöhr AM, Lankes E, Kühnen P, Schnabel D, Ernert A, Stäblein W, Craig ME, Blankenstein O, Grüters A, Krude H

Abstract
Context: The optimal levothyroxine (LT4) dose required to treat congenital hypothyroidism (CH) remains unclear, with a debate if higher starting doses (>10µg/kg) are necessary and safe for normal Intelligence Quotient (IQ).
Objective: To examine the psychomotor, metabolic and quality of life outcome in patients with CH treated with a mean high initial LT4 dose.
Design, settings, participants: A cross- sectional cohort study of CH patients identified in the Berlin newborn screening programme from 1979-2003. Total of 76 CH patients (mean age 18 years, mean initial LT4 dose 13.5µg/kg) and 40 siblings completed the study.
Main outcome measures: Psychomotor (Wechsler Intelligence Test, CNS Vital Signs), quality of life (QoL, SF 36 Health Survey), anthropometric (BMI, height) and metabolic (Intima Media Thickness, laboratory parameters) outcomes were compared to healthy siblings. Mean values and percentage of episodes of elevated T4, T3 and suppressed TSH before age two years were analysed. A meta- analysis of treatment CH studies was performed.
Results: There were no significant differences in IQ, QoL or other outcome measures compared with controls. The majority of T4 levels were high before age two years and during subsequent testing, but mean T3 and TSH levels remained normal. The meta-analysis showed a significant IQ difference in severe versus mild CH cases only if treatment started with a LT4 dose < 10µg/kg.
Conclusions: High initial LT4 dosing is effective and safely achieves optimal cognitive development in CH, including those severely affected. Supra-normal T4 values during infancy are not associated with impaired IQ in adolescence.

PMID: 29325045 [PubMed - as supplied by publisher]

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