Congenital Thyroid Binding Globulin (TBG) deficiency. Its incidence on a screening program for neonatal hypothyroidism: 92

Abstract

Service de Gēnētique et Maladies Hērēditaires du Mētabolisme de l'Enfant - LILLE (F) - Congenital Thyroid Binding Globulin (TBG) deficiency. Its incidence on a screening progrom for neonatal hypothyroidism. - During 13 months, 76650 newborn infants have been screened for congenital hypothyroidism by blood spot T4 and TSH measurements at 6 days of life.Twelve cases of TBG deficiency were detected,indicating prevalence of 1/6,400 births. Follow-up data on these children are reported: (1)patients: 11 males and 1 female without clinical symptoms obvious of hypothyroidism.(2) at 30 days of life: (a) TBG RIA concentrations (TBGKR), CEA)were between 2.4 and 13.2 μg/ml; in 9 males TBG was between 2.4 and 7.5 μg/ml and in the 2 remaining males 10.9 and 13 μg/ml; in the girl TBG level was 13.2 μg/ml (mean control value 39.2 ± 8.3 μg/ml) (b) T4 values were always low: 1-6 μg/100ml (mean normal value 12.7 ± 3.06).(c) T3 values were between 37 and 145 ng/100ml, mean value was 102.75 (mean normal value: 229.19 ± 45.01).(d) Resin T3 uptake was always high: 53 to 74%, mean value 71% (normal: 36.3 ± 3.59.(e) Free T4 index (FTI) varied: normal in 5 cases, decreased (<2.1) in 7 cases.(f) TSH levels were normal (< 9 μU/ml)(g) T4/TBG ratio increased in 10 cases: 0.37-1.66 and was normal in 2 cases:0.34 and 0.25 (normal mean value 0.31 ± 0.05, normal range 0.21 - 0.37). In summary, 1) the incidence of the TBG deficiency was higher than reported by DUSSAULT (1/13,000).2) Severe TBG deficiency resulted in some disturbances in the measurements of thyroid hormone which might suggest hypothyroidism.3) The male predominance (11/12) and the reduced TBG level in mothers (2 families studied) were consistent with X-linked transmission.