EFFECTS OF MARGINAL IODINE DEFICIENCY DURING PREGNANCY - IODIDE UPTAKE BY THE MATERNAL AND FETAL THYROID

Iodide uptake by the thyroid is an active process. Iodine deficiency a nd pregnancy are known to influence thyroid hormone metabolism. The ai m of this study was to clarify the effects of iodine deficiency and pr egnancy on iodide uptake by the thyroid. Radioiodide was injected intr avenously into nonpregnant and 19-day pregnant rats receiving a normal or marginally iodine-deficient diet. The uptake of radioiodide by the thyroid was measured continuously for 4 h. The absolute iodide uptake by the maternal and fetal thyroid glands at 24 h was calculated by me ans of the urinary specific activity. Pregnancy resulted in a decrease in the absolute thyroidal iodide uptake. Marginal iodine deficiency h ad no effect on the absolute iodide uptake by the maternal thyroid. Th e decreased plasma inorganic iodide was compensated by an increase in thyroidal clearance. A similar compensation was not found for the fetu s; the uptake of iodide by the fetal thyroid decreased by 50% during m arginal iodine deficiency. This can lead to diminished thyroid hormone production, which will have a negative effect on fetal development, e specially of the brain.