Congenital Hypothyroidism and subsequent language disorders

S Langham

Great Ormond Street Hospital, London

Endocrine Nurses Training Course 9-11 September 2004
Wills Hall, Stoke Bishop, Bristol, BS9 1AE

Introduction

With the introduction of screening programmes in the late 1970’s for congenital hypothyroidism (CH), children with early treated CH can now expect to achieve normal neuro-cognitive development. However, long-term studies report that some children, usually with the most severe disease, perform consistently below age-matched controls on a variety of psychological measures, including IQ, motor skills, visuo-spatial skills, arithmetic, attention, memory and language. Various factors including aetiology, skeletal maturation, thyroxine concentrations at diagnosis, initial thyroxine dose, age at commencement of treatment and long-term control have been examined in relation to outcome. This study examines the cognitive and language development (using parent completed questionnaires) of a group of early treated children with CH and compares the CH group to age matched controls and also to normative data.

Method

Parents of 16 CH children (mean age 30 months, range 23-39 months) and 8 age-matched controls (mean age 28.3 months, range 23-34 months) completed the two questionnaires assessing the verbal and non-verbal skills of their child. For convenience, the children were divided into two age groups according to the language questionnaire completed: group 1 (23-30 months) completed the MacArthur Communicative Development Inventory – Words and Sentences (MCDI W&S) and group 2 (31-39 months) the MacArthur Communicative Development Inventory – level III (MCDI-III). The MCDI’s are designed to assess emerging and current language skills, including the child’s vocabulary and sentence construction and in addition, the MCDI - W&S assesses the child’s use of irregular nouns and verbs, references to past/ future events, references to absent objects or people, use of suffixes and mean sentence length. Cognitive development was assessed with the Parent Report of Children’s Abilities (PARCA) for two year olds.

Results

Children with CH performed at similar levels to controls and standardised data on the cognitive measure but performed significantly below controls and normative data on measures of vocabulary and sentence complexity, indicating some difficulties for the CH group as a whole with language development. Children in study group 1 also achieved significantly lower mean scores on use of irregular nouns and verbs and mean sentence length. The older children in study group 2 did not demonstrate significant language delay.

Differences between group 1 and 2 on initial thyroxine dose and age at start of treatment approached significance, with group 1 on average receiving 1.3µg/kg/day less than group 2 and on average starting thyroxine 3 days later. It was not possible to demonstrate a significant relationship between language development and initial thyroxine dose or language development and age at start of thyroxine treatment. This may have been because of the small numbers of children in the study sample.

Discussion

The two year old children with early treated CH in this study demonstrated a significant deficit in language skills and this, combined with the normal cognitive skills presents a similar profile to children with expressive language disorder and specific language impairment. Such children are at risk for future difficulties in school and perform below controls on a variety of psychological measures in the teenage years, also achieving less academic qualifications than peers. Early identification of language delay is therefore extremely important for children with CH, in order to enable early and appropriate intervention so that long-term risks are minimised. A larger study is probably required to determine if initial thyroxine dose and/ or age at start of thyroxine treatment influences the scores achieved on the language domains measured by the MCDI’s.

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