Endocrine Abstracts

Children with congenital hypothyroidism (CH) due to anatomical defects (AD) have different thyroid hormone levels at presentation from those with dyshormonogenesis (DH). We set out to explore these differences at initial presentation and at follow up. We also compared calcitonin levels and growth in these subjects with healthy controls. Data for the CH children were collected from hospital notes for birth weight, gestation, sex, initial laboratory thyroid function, starting dose of thyroxine and imaging results. CH children were categorized as AD (agenesis, ectopia) or DH. All data are mean (sem) unless otherwise stated. We studied 38 children with CH (13 boys), median age (range), 9.7 (1.1–17.2) years, 11 with DH and 27 with AD and compared them with 71 age and sex-matched controls (40 boys), 10.1 (0.6–17.8) years. DH babies had lower birth weight SDS’s corrected for gestation than those with AD, mean (S.D.): −0.78(1.0) vs +0.23(0.9), P=0.01 and subsequent weight and height SDS’s were lower in CH than controls. Initial TSH values were higher in AD 129 (8.6) versus DH 8.8 (22.2) mU/l, total T₄ levels were lower in AD 81 (12.3) versus DH 16.6 (20.3) pmol/l. At 8.3 years, the only significant difference was in the thyroxine dose: AD 86 (5.3) versus DH 59 (6.5) μg, P=0.004. CH children had higher FT₄ levels than controls: 17.9 (0.58) vs 13.8 (0.22) pmol/l, P<0.0005; and higher TSH levels 4.6 (0.74) vs 1.96 (0.14) mU/l, P=0.003. Calcitonin levels were significantly lower in CH than controls P<0.001 with a trend towards lower levels in AD versus DH. CH children are small and remain small in childhood even after treatment. Calcitonin levels are significantly lower in CH children compared to controls. Differences exist amongst subgroups of CH children in thyroid hormone levels; AD have higher initial TSH and lower T₄ levels and require higher doses of L-Thyroxine. Differences persist during childhood in thyroid hormone levels in treated CH children compared to healthy controls.