25 METABOLISM OF a FETOPROTEIN IN CONGENITAL HYPOTHYROIDISM

Abstract

a-Fetoprotein (a-FP) levels are increased in congenital hypothyroidism (CH) for unknown reasons. To explore this, we studied the half-life of a-FP during the first month of life in neonates with CH and neonates with transient hyperthyrotropinaemia (TH), which we considered as the control group. Between the 3rd and 7th day of life a-FP was measured in 60 cases with CH with a mean gestational age of 39.9±1.5 weeks and in 184 cases with TH with a mean gestational age of 39.3±1.9 weeks. The mean log a-FP levels in the two groups were 4.35±0.39ng/ml and 3.97±0.36ng/ml respectively (p<0,01). Levels of a-FP were also measured in 61 cases with CH at a mean age of 29.8±12.9 days and in 37 cases with TH at a mean age of 36.5±13.1 days. The respective mean values of log a-FP were 3.84±0.46ng/ml and 2.71±0.55ng/ml, after adjustment for conceptional age differences (p < 0,001). The half-life of a-FP was 15.7 days for the CH group and 7.7 days for the TH group. The half-life of a-FP was also calculated in each of 39 cases with CH and 8 cases with TH for which there were serial measurements of a-FP. The half-life of a-FP in the two groups was 12 days and 4.9 days, respectively. We conclude that catabolism of a-FP is delayed in CH group, resulting in inceased serum levels of a-FP. The lack of thyroid hormones, and especially of T3, is probably responsible for that.