Low Dietary Iodine Intake and the Functional Activity of the Rat Thyroid 1 2

Abstract

Summary

The effects of low dietary iodine intake on the functional activity of the thyroid were studied in young female albino rats. The low iodine diet contained 0.05 ppm iodine, with casein as the primary protein source. Feeding this diet to 30-day-old rats for periods of up to 3 months increased the thyroid hormone secretion rate (TSR). The FBI was within the normal range but thyroid size was slightly increased as compared to the corresponding control rats of the same age fed Purina Lab Chow. On the low iodine diet, the percentage uptake of thyroidal-¹³³I was greatly increased, and the biological half-life of thyroidal-¹³¹I was significantly reduced, indicating a faster turnover of thyroidal-iodine (hormones). The DNA content of the thyroids indicated hyperplasia and hypertrophy suggesting stimulation of the gland. It was concluded that under these experimental conditions the rat thyroid has the capacity to increase its activity to compensate for any moderate low dietary iodine for at least 3 months by augmenting recycling mechanisms and thyroidal turnover of hormones.