The Effects of Maternal Hypothyroidism on the In Vitro Metabolism of [1-¹⁴C]-Glucose in Rats[*]

Abstract

The in vitro metabolism of tissue slices from 22 day pregnant, surgically thyroidectomized rats was studied. The fetuses of these animals have been shown previously to have depressed serum glucose, serum protein and liver protein and glycogen levels.

The maternal livers of the hypothyroid animals show an in vitro metabolism typical of hypothyroidism. However, the fetal livers are very different from the maternal livers in their glucose utilization. The livers of these fetuses of hypothyroid mothers show greater in vitro uptake and utilization of glucose than the fetuses of controls. The fetal liver fractional distribution of this glucose among the four compartments measured - CO₂, glycogen, protein and lipid - is not significantly altered by the treatment. The failure of these fetuses to accumulate liver glycogen normally is obviously not due to an inability to synthesize glycogen but rather is due to higher glycogen turnover and possibly insufficient or inappropriate substrate levels. These fetuses have the capacity for lipid and protein synthesis from glucose and the in vitro incorporation into these components is greater than normal. The in vitro liver metabolism in the fetuses of hypothyroid mothers is not indicative of fetal hypothyroidism and, in fact, suggests fetal hyperthyroidism at this period of gestation.

Key words

Glucose Metabolism - Hypothyroid - Hyperthyroid - Fetal - Placental - Maternal

1 Supported by Biomedical Sciences Support Grant, DHEW-5505-R07024-9.

1 Supported by Biomedical Sciences Support Grant, DHEW-5505-R07024-9.