ESPE Abstracts (2019) 92 P1-288

Outcomes of Persistent Hyperthyrotropinaemia in Well Term Infants

Sze Ng1,2, Nancy Katkat1, Tal Oryan1, Kayode Ayoade1, Mahreen Aleem1

1Southport and Ormskirk Hospitals NHS Trust, Southport, United Kingdom. 2University of Liverpool, Liverpool, United Kingdom

Background: Neonatal hyperthyrotropinaemia (HT) is defined by elevated thyroid stimulating hormone (TSH) and normal free-thyroxine (FT4) level. Persistent HT in the neonatal period is often a diagnostic dilemma for clinicians to either treat to prevent subclinical hypothyroidism or to wait and monitor thyroid function tests (TFTs).

Methods: As part of an audit, 1,449 term infants who had TFTs undertaken as part of a prolonged jaundice screen from 2012-2017 were reviewed. Infants with HT (defined by TSH>5mU/L) were followed up in clinic. We evaluated perinatal factors and TFTs were monitored in 2-4 weeks, then regularly 2-4 monthly until 2 years of age or until HT resolved.

Results: There were 37 term infants (27 males) with a raised TSH (>5mU/L) and normal FT4 level over the 5-year period. This represents 2.6% of the 1,449 term infants found to have HT. All infants with HT were born in good condition. Mean gestation was 38.1 weeks (±2.1 SD, range 33.1-42.0). 4 infants had Trisomy 21 and 3 infants had a maternal history of hypothyroidism. In 2 infants, we started levothyroxine treatment due to rising TSH and falling FT4 levels. 9% of infants had TSH normalised to 5mU/L in 4 weeks without treatment, 54% normalised their TSH in 8 weeks, 83% normalised in 3-6 months, 94% normalised in 12 months and 1 patient had persistent TSH >5mU/L which did not require treatment at 24 months.

Conclusions: In 95% of all the cases of HT in well term infants, the natural course was that the TSH resolved to normal < 5mU/L by 2 years of age. In 3% of cases, TSH remained elevated (> 5mU/L) at 2 years but FT4 levels were normal and in the upper quartile range (>15pmol/L) without treatment. We recommend TFTs monitoring due to the risk of decompensation although the risk of decompensation is low; and frequency of monitoring can be reduced after 2 years.

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