Endocrine Abstracts

An enlarged neck mass (20x18mm), anterior to spine was incidentally discovered in foetal 20-week anomaly scan, with neck fixed in hyperextended position throughout the scan. Mother (G2P1) was asymptomatic without thyroid under or overactivity; maternal baseline thyroid function and thyroid antibodies were negative. At 21-weeks, the small stomach bubble confirmed oesophagus was compressed and swallowing compromised, with high(ish) amniotic TSH (8.5). MDT opinion was foetal blood sampling and foetal treatment with mother’s consent. The treatment benefits for large goitre are foetal survival, reduced goitre size, facilitate safe delivery at term, and facilitate intubation if preterm birth occurred. Foetal neurodevelopmental benefits are very likely, but unable to document. The challenges were associated risks with repeated interventions (amnio/cordocentesis), preterm delivery and uncertainties around optimum thyroxine dose to reduce foetal goitre and interpreting foetal results. After careful consideration, IV thyroxine at 10 mg/kg on estimated foetal weight, for 10 days, to be administered once every 2 weeks was chosen. Foetal treatment commenced at 23-weeks (15.03.2024), with goitre of 25x13mm. 50 mg of IV thyroxine (estimated foetal weight 0.5 kg) was administered via cordocentesis, and foetal blood confirmed profound hypothyroidism (TSH >100, FT4 3.9 & FT3 1.5) and gene panel testing identified compound heterozygous mutation in foetal thyroglobulin gene. Mum was started on 50 mg thyroxine daily, to supplement intrauterine transfer. Foetal goitre was monitored regularly with 2 weekly intra-amniotic thyroxine administration. At 33-weeks (24.05.2024), goitre has remained stable (24x16mm) and now less significant in relation to foetal size. The foetus can completely flex the head, trachea is patent without goitre pressure, stomach bubble is normal in size, without polyhydramnios. Repeat cord blood shows improved thyroid function (TSH >100, FT4 8.5, FT3 2.1), with stable maternal thyroid function. In summary, foetal goitre size has not increased; foetal thyroid function has improved; mother, pregnancy & foetus have continued to thrive confirming effective & safe intra-uterine thyroxine treatment. 33-week scan suggests a normal vaginal delivery is possible, without need for an EXIT procedure. An MDT approach with ENT, Neonatal and Obstetric teams is underway at Brighton (with tertiary support) for safe delivery of this baby, sometime in July 2024.