Neurocognitive function in children with compensated hypothyroidism: lack of short term effects on or off thyroxin

BACKGROUND: Although thyroxin therapy clearly is beneficial to children with frank hypothyroidism there is little data on the effects of thyroxin in children with compensated or subclinical hypothyroidism. The objective of this study was to determine the effect of thyroxin therapy on cognitive function in children with compensated hypothyroidism. The hypothesis was that thyroxin therapy would change neuropsychological function. METHODS: Eleven patients with a history of sub clinical hypothyroidism entered the study. At the start of the study, six out of the 11 were on thyroxin therapy, while 5 were off therapy. All patients underwent a battery of neuropsychological testing and thyroid function tests at the start of study. Based on the results of thyroid function tests, two of the 5 patients who were off thyroxin were started back on thyroxin. All of the 6 patients who were on thyroxin were taken off thyroxin. All patients then underwent repeat neuropsychological testing and thyroid functions after an average of 91 days. RESULTS: Thyroxin therapy could not be shown to have an effect on neuropsychological function in this short term study. Our patients had attention problems as compared to the normal population. No significant differences were found between our subjects and normal population standards in verbal processing, visual processing, motor speed/coordination and achievement. CONCLUSION: In this small, short term study, thyroxin therapy could not be shown to affect neuropsychological function in children with compensated hypothyroidism. These children may have attention problems but appear to have normal verbal and visual processing, motor speed/coordination and achievement

Linear growth in early treated children with congenital hypothyroidism

Length/height was studied from birth to 6 years of age in 103 children with congenital hypothyroidism identified by the Norwegian or Swedish screening programs. We used the 'infancy childhood-puberty (ICP) growth model'. This model describes normal linear growth during the first 3 years of life by an infancy component with the addition of a childhood component, the latter acting from the second half of the first year. In comparison with reference children, children with hypothyroidism had reduced growth from 6 to 12 months, and increased growth after 12 months of age. Mean onset of the childhood component of growth was delayed from 8.1 months (SD 1.9) to 10.4 months (SD 2.2) in girls, and from 8.9 months (SD 2.0) to 11.0 months (SD 2.1) in boys. Age at onset of the childhood component was correlated with age at start of treatment (r=0.24), and in children with more severe hypothyroidism (pretreatment serum thyroxine <40 nmol/l) inversely correlated with the L-thyroxine dose at start of treatment (r = -0.40). Change in height standard deviation score from 1 to 3 years of age was correlated with the serum thyroxine concentration at age 1 year (r = 0.30). The delay in the onset of the childhood component of growth and the association with age at start of treatment and initial (L)-thyroxine dose indicate that thyroid hormones during the first months of life are essential for normal onset of the childhood component of growth, which otherwise is assumed to be growth hormone dependent.link_to_subscribed_fulltex