Faculty

Loo Ling Wu

Congenital hypothyroid Screening – Can we do better?

Thyroid hormones play a critical role in neurogenesis and myelination of the nervous system during the foetal and postnatal period. Congenital deficiency of thyroid hormones leads to permanent neurological damage and mental retardation in children. Early diagnosis and treatment had been shown to prevent neurological damage and restore normal IQ. Hence biochemical screening of all newborns is crucial, as signs and symptoms of congenital hypothyroidism are not apparent at birth until months later. Newborn screening for congenital hypothyroidism was implemented in Malaysia in 2003. Since inception, there had been much challenges including variation in interpretation of thyroid function, criteria for diagnosis and management of the condition. Special categories of babies such as the preterm, low birth weight and sick newborns where the thyroid physiology is different have not been appropriately addressed. Management from screening to post-screening has been very much dependent on the understanding and experience of the attending doctor. Hence the standard of care is very variable.

A working group consisting of paediatric endocrinologists was initiated to develop a national consensus guidelines based on scientific evidence taking into account the Malaysian demographics, limited resources, technology and paucity of local data. This guidelines provides a comprehensive, step-by-step approach and recommendations from screening through diagnosis to management of congenital hypothyroidism.

We recommend primary TSH with supplementary FT4 as the screening strategy, on cordblood collected at birth. As 99.6% of all deliveries in Malaysia are conducted in the hospitals, screening using cordblood is probably the most effective way to ensure complete coverage of all deliveries in the country. A cut-off TSH of >60 mU/L is used to recall babies for confirmatory re-testing. Babies with borderline TSH >20 to <60 mU/L are also recalled if concomitant FT4 is ≤ 15 pmol/L. These cut-off values are derived from previous small local studies and consensus expert opinion. Recall is done on Day 4-6, at least 72 hours after birth to avoid the period of physiologic TSH surge. At recall venous blood is taken for re-testing of TSH and FT4. Results are usually confirmatory in most cases. Elevated TSH is the primary determinant for diagnosis and initiation of treatment. In babies with borderline TSH, concomitant FT4 would be the determining factor. We emphasize the importance of taking into consideration all TSH and FT4 values and their trends in our decision to treat or to monitor. It is not unreasonable to err toward treatment before confirmatory results are available for families with logistic or socioeconomic issues. This guidelines give details on initiation of treatment and follow-up to avoid under or over treatment. Re-evaluation is done at 3 years, to identify those with permanent congenital hypothyroidism who need continuation of LT4 for life. Thyroid scintigraphy and thyroid ultrasound may be considered for these patients to determine the aetiology. A special categories of babies are highlighted. Post-screening strategies are recommended for this group of babies.

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