Most newborn infants with TSH elevation have permanent congenital hypothyroidism but a minority have transient dysfunction. Accurate, early diagnosis is desirable in order to counsel parents effectively, select patients who require further study (including molecular genetics), and formulate a management plan (e.g. lifelong treatment, initial treatment for first 3 years of life then re-evaluation).
Aim To determine the diagnostic accuracy of combined ultrasound and isotope thyroid (dual) scanning carried out during a single visit following initial assessment and thyroxine treatment for TSH elevation.
Methods Retrospective, blind review of infants undergoing dual scanning between 2004-2011 in a single centre.
Results 88 infants (54F:34M), median (range) birthweight and gestation 3.4 (2-4.9) kg, 40 (33-42) weeks had both scans performed at 18 (12-56) days. Definitive diagnosis at the single visit was possible in 72 (93%) infants, the causes being thyroid ectopia (38), athyreosis (14), hypoplasia (2 - one due to homozygous TSH-R, one to heterozygous PAX-8 mutation) and dyshormonogenesis (18 - 4 thyroglobulin, 3 thyroid peroxidase, and one THOX-2 mutation). Of the 16 remaining children 8 had transient TSH elevation and have stopped treatment (one had confirmed maternal blocking antibodies, two were heterozygotes for TSH-R mutation), while 8 await a trial off thyroxine treatment when aged > 3 years (Down syndrome , Turner syndrome , suspected blocking antibodies , TSH-R heterozygote ). Of note, isotope scan showed no uptake in 2 of the transient group and in 4 of the 8 children awaiting a trial off thyroxine.
Conclusion Dual scanning is highly effective in making a definitive diagnosis in newly referred infants with TSH elevation. The finding of an in situ gland on ultrasound helps to direct molecular genetic study. Isotope scanning alone may be misleading in a minority of cases. We believe that the families of newborn infants with TSH elevation should be offered the opportunity to undergo dual scanning in a specialist centre.