A comparison between the neurological and intellectual abnormalities in children and adults with congenital hypothyroidism

Abstract

Standardised intellectual, motor and behavioural tests have been undertaken in a group of 73 children and 43 adults with congenital hypothyroidism in a regional study in the north of England. These provide comprehensive data with which to compare the results of studies of children diagnosed by screening and indicate the degree of abnormalities persisting into adult life in those patients diagnosed before screening was introduced. The mean IQ scores of the hypothyroid children and adults were 1-2 standard deviations (SD) below the population means. Longitudinal IQ data indicate persistence of intellectual abnormalities, though there was an increase in IQ score in several patients. The mean motor scores were reduced by 1-2 SD in the children and 1-3 SD in the adults. Behavioural problems and personality difficulties mainly of a neurotic nature also persisted into adult life.

Prevention of intellectual disability through screening for congenital hypothyroidism: how much and at what level?

“…The percentage with IQ <70 was 26.6% in one study30 and not reported in the other 28 29. Of 112 school-aged children with CHT in the first study, 32 (28.6%) attended special schools for learning disability, including three in residential schools 30.…”

“…Two comprehensive CHT surveillance studies conducted in southern and northern England prior to the introduction of screening reported prevalence estimates of clinically detected CHT of 1 in 6700 28–30. One of the two UK studies collected complete data from healthcare providers in Kent and East Sussex in southeastern England and reported a prevalence of 1 in 6700,30 the same figure as in the Swedish retrospective screening study 27…”

“…The same study reported that two of 132 children of all ages with probable CHT resided in long-term care facilities. In the second English study, one of 45 children with CHT had an IQ score of 40; apparently all others had an IQ >50 29. If one pools the data from the three studies that reported the distribution of IQ scores, 4.5% of children with clinically diagnosed CHT had IQ <50.…”

“…Equally importantly, even children with unscreened clinical CHT who have IQ scores in excess of the 70–75 range used to classify a child as having disability incur serious cognitive impairment. The mean IQ score reported for children with clinical CHT was 82 in the two UK studies,29 30 and 87–88 in the two Swedish studies 26 27. A Japanese study, which was excluded from table 2 because of a lack of detailed information about the sample composition, reported a mean IQ of 87 for 22 children aged 36–66 months who had been tested using various instruments 35.…”

ENDOCRINOLOGY AND ADOLESCENCE: Congenital hypothyroidism: a clinical update of long-term outcome in young adults

“…In series of patients studied before the introduction of neonatal screening, major differences in clinical characteristics were found between patients with different degrees of intellectual disability (15,16,17,18) and about one-quarter of children with clinically diagnosed CH have overt neurodevelopmental deficits (19).…”