Altered maternal thyroid function: fetal and neonatal myocardial metabolism.

The influence of the maternal thyroid status on the fetal and neonatal myocardial protein, carbohydrate and lipid metabolism was studied in rats. The neonates born of hypothyroid mothers could not survive beyond 8 days after birth. The offsprings born of hypothyroid mothers showed growth retardation, decreased level of heart mitochondrial protein, reduced myocardial free fatty acid (FFA) oxidation at birth and afterwards, low glucose oxidation by the heart at later fetal stages, and afterwards, despite low heart glycogen reserve, glucose oxidation was high. The offsprings born of hyperthyroid mothers showed stimulation in overall growth, increased myocardial FFA oxidation and increased 14C-glucose incorporation into glycogen as well as increased myocardial glucose oxidation during fetal stages. Results indicate that maternal thyroid hormones play an important role in the metabolic control of fetuses and neonates.