Endocrine Abstracts

Background: Among infants presenting with prolonged hyperbilirubinaemia there is anecdotal evidence that some babies who were Newborn Screening-negative for congenital hypothyroidism (CHT) have CHT diagnosed at the time of presentation with jaundice.

Aims: To determine the prevalence of CHT in babies presenting with prolonged jaundice and to assess the predictive value of lowering the TSH cut-off for a screen-positive result on the ability to identify babies at the time of newborn screening (NBS) who might subsequently present with hyperbilirubinaemia and abnormal thyroid function tests (TFTs).

Methods: We investigated infants presenting with prolonged neonatal jaundice (serum bilirubin >100 μmol/l at >2 weeks of age) to assess the prevalence of CHT among cases referred to a regional paediatric hospital over a 2-year period (Apr 07–Mar 09). The NBS record and serum TFTs were checked to identify those who were either screen positive (bloodspot TSH level >20 mU/l), ‘persistent borderline’ (2 bloodspot TSH 8–20 mU/l) or were found to have serum TFTs within the hypothyroid range.

Results: A total of 257 infants presented with prolonged jaundice, of whom 179 (70%) had serum TFTs. Five infants had a serum TSH >10 mU/l (range 11–422 mU/l, fT4<4–22 pmol/l), bloodspot TSH in this group was 0.5–227 mU/l and two of these were identified as CHT screen positive A further 39 had serum TSH 5–10 mU/l (fT4 14–28 pmol/l), all had NBS TSH results <8 mU/l (0.4–4 mU/l). All children other than those identified as screen positive had normal follow up TSH levels and none were found to have CHT at 3 months of age.

Conclusions: Among our cohort of infants presenting with prolonged jaundice, there were only 2 children with confirmed CHT (prevalence of 0.79%). We conclude that the current NBS blood spot TSH cut-off >8 mU/l is a robust screening tool for CHT that prevents the occurrence of false negatives.