ESPE Abstracts

Backgrounds: The prevalence of congenital malformations (CM) is higher in infants referred with capillary (c) TSH elevation on newborn screening. However, establishing the prevalence of CM ± dysmorphic syndromes in true congenital hypothyroidism (CH) requires careful distinction between true and transient CH.

Objective: To determine the prevalence of CM ± dysmorphic syndromes in all infants referred with TSH elevation on newborn screening in Scotland since 1979 according to strictly defined diagnostic categories and dividing infants with CM into cardiac, extra-cardiac, cardiac and extra-cardiac ± associated syndromes (including Down (DS) and unclassified (UC));and infants with syndromes without accompanying CM.

Methods: The diagnostic categories were: i) Definite CH: thyroid dysgenesis or dyshormonogenesis on imaging, or venous (v) TSH >50 mu/l and TT₄/fT₄ subnormal in an otherwise healthy term infant, or vTSH >10 mu/l on LT₄ replacement after first year of life; ii) Probable CH – vTSH >50 mu/l with normal TT₄/fT₄ in a healthy term infant; iii) status uncertain – criteria for true and probable CH not met, infant unwell ± CM and/or dysmorphism; iv) Transient TSH elevation – cTSH elevation with subsequent normal thyroid function off treatment.

Results: Between August 1979 and March 2014 903 infants were referred with cTSH elevation and categorised as Definite (548), Probable (41) CH, status uncertain (97), and Transient TSH elevation (182) (data insufficient in 35). Breakdown of CM in the Definite CH group was:cardiac 7 (1.2%) (1 DS); extra-cardiac 14 (2.5%), cardiac and extra-cardiac 2 (0.4%), syndromes 8 (1.4%) (Pendred (2), PTH resistance (2), Sotos, Beckwith, Translocation 14/15, UC); for the Status Uncertain group: cardiac 17 (17.5%) (11 DS, DiGeorge, Williams), extra-cardiac 6 (6%), cardiac and non-cardiac 9 (9%) (6 DS, trisomy 18, UC), six syndromes (all DS); and for the Transient TSH elevation group: cardiac 7 (3.8%) (2 DS), extra-cardiac 19 (10.4%) (DS 2, UC), cardiac and extra-cardiac 6 (3.3%) (DS 2,UC), syndromes 3 (1.6%) (Turner, Kabuki, UC).

Conclusion: The prevalence of cardiac and all CM for true CH in Scotland is 1.2 and 5.6% compared with 0.8 and 2.6% for European population. This is much lower than for Transient TSH elevation (19.2%) and Status Uncertain (39%) and underlines the need for rigorous diagnosis, with retesting of doubtful cases after 3 years of age.