Poster Presentation ESA-SRB-APEG-NZSE 2022

Neonatal hypothyroidism: factors associated with the diagnosis of transient vs permanent hypothyroidism and management at a tertiary Australian centre   (#461)

Annabelle Hobbs 1 2 , Michelle Jack 3 , Paul Benitez 1 3 , Shubha Srinivasan 1 3 , Tiffany Wotton 4 , Yoon Hi Cho 1 3
  1. Department of Endocrinology, Children's Hospital Westmead, Sydney, New South Wales, Australia
  2. Department of Endocrinology, Queensland Children's Hospital, Brisbane, Queensland, Australia
  3. Discipline of Child and Adolescent Health, Children’s Hospital Westmead Clinical School. Faculty of Medicine and Health, The University of Sydney, Sydney, New South Wales, Australia
  4. NSW Newborn Screening Programme, Children's Hospital Westmead, Sydney, New South Wales, Australia

Aim

Congenital hypothyroidism, when identified in hospitalised neonates, may be either transient (TCH) or permanent (PCH).  We aimed to describe the investigation and management of these infants and identify associated variables.

Methods 

Data were extracted from handover documents and electronic medical records on infants with suspected hypothyroidism between 1/7/2019 and 30/6/2021. 

Results 

Of 124 infants (57% male) who met inclusion criteria, 43.3% were premature (<37 weeks gestation).  There was a high rate of infants with common neonatal comorbidities including jaundice (61.9%), respiratory distress (64.1%) and hypoglycaemia (37.5%).  45.1% had cardiac anomalies and 18% had a syndrome such as trisomy 21, 22q11, or other genetic abnormality.

Median TSH at referral was 10.5mIU/L [IQR 3.8-24] at a median age of 28.5 days.  In those who had presumed TCH, thyroid function tests (TFTs) demonstrated both a significantly lower TSH (7.32mIU/L [3.3-12.8] vs 83.8mIU/L in PCH [9.8-270] (p=0.01)) and higher FT4 (12.4pmol/L (10.15-16.75) vs 8.6pmol/L (8.1-13) vs (p=0.017)).   80% of nuclear medicine scans performed were abnormal, demonstrating either dyshormonogenesis or dysgenesis, compared to only 29.3% of thyroid ultrasounds revealing abnormalities.

The working diagnosis was TCH in 73/117 (62.4%), and PCH in 25/117 (21.4%).  NBS TSH levels were significantly higher in those with presumed PCH.  36% of those with presumed PCH were not identified through the NBS and were diagnosed through formal TFTs for clinical indications in the hospitalised infants.

Levothyroxine, at an average dose of 8.7mcg/kg/day, was commenced in 65.8% of infants. At last review only 11/77 infants had ceased therapy. Duration of this therapy varied widely between 10 days to 15 months. 

Conclusion 

TFT abnormalities are common in unwell infants. While most were presumed to have TCH, the majority were nevertheless commenced on thyroxine treatment. Further prospective studies are required to develop predictors to differentiate between transient and permanent CH and guide treatment.