Neurodevelopmental Outcomes in Congenital Hypothyroidism

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Kempers et al examined cognitive and motor function in young adults with congenital hypothyroidism (CH) born during the first 2 years after the introduction of the Dutch neonatal screening program. Seventy patients (median age of 28 days at start of T₄ supplementation; females n = 55, 79%) were evaluated and separated into 3 groups according to the severity of the CH: severe (n = 35), moderate (n = 16) or mild (n = 19). Patients with severe CH had significantly worse (higher) motor scores and (lower) full-scale and performance intelligence quotient (IQ) scores than the normal population. No significant changes were detected in IQ and in motor score classification from childhood to adulthood nor in the severity of the disease. However, the starting date of treatment, correlated with these 2 parameters. The authors concluded that cognitive and motor deficits appear to persist into adulthood in severely affected patients with CH who started treatment relatively late (at a median age of 28 days) and with lower thyroxine doses than those advised in more recent years.

Kempers MJE, van der Sluijs Veer L, Nijhuis-van der Sanden MWG, et al. Intellectual and motor development of young adults with congenital hypothyroidism diagnosed by neonatal screening..J Clin Endocrinol Metab. 2006;91:418–424.

Editor’s Comment

Thyroid hormones play an essential role in brain development both during pre-and postnatal life. The prenatal thyroid hormone state is dependent on maternal-fetal thyroid hormone transfer and on fetal thyroid hormone production from the second trimester onward. Shortening the postnatal phase of hypothyroidism has been shown to be highly effective in diminishing cognitive and motor deficits of patients with CH. This recent study by Kempers et al is only the second one to report on the long-term outcome of young adult patients with CH, as previous outcome studies only reported data until late childhood. These authors have clearly shown that cognitive and motor deficits persist in CH patients, particularly in those subjects who are severely affected (initial T₄ levels of less than 2.3 μg/dl at the time of thyroid screening), but outcome was not related to the age at which T₄ treatment was initiated (Table). One must bear in mind, however, that these deficits appear to persist into adulthood mainly in severely affected patients with CH who were diagnosed and started on treatment relatively late and who were treated with lower thyroxine doses than those advised in more recent years.

Characteristics of the subgroups with different severities of CH

Cognitive deficits in patients with severe forms of CH have also been recently published in 2 studies by Selva et al¹ and Bongers-Schokking.² Children with moderate CH were found to have higher full-scale IQ scores than subjects with severe CH, regardless of the initial treatment dose. Initial L-thyroxine dose and faster time to normalization of thyroid function were found to be important to optimal neuro-developmental outcome. An initial dose at the higher end of the recommended range seems to be important for the improved outcome of children with CH, particularly those with severe forms of the disease, as initial and subsequent suboptimal treatment of CH leads to cognitive and motor deficits.

Roberto Lanes, MD

References - (linked to )

Last Updated: 04/30/2008