Metabolism of radioiodide by lactating goats given 131I for extended periods

Twenty-two goats were given twice-daily doses of 131I to determine distribution of radioiodine into milk, urine, feces, and thyroids as these animals approached steady state. For 16 goats on the control diet 36.7 and 5.6% of a daily dose of 131I per liter was found in the milk and plasma, respectively. The 131I milk-plasma ratio was 7.6. Supplementing the control diet with 4 mg of iodine per day resulted in a reduction of thyroid ~31I and an increase in milk 1~1I in milk, whereas :1.2 g of KI per day markedly reduced the lalI in milk and reduced the M/P ratio by a factor of 10. Perchlorate, fiuoroborate, thiourea, Chlorothiazid, and thyroxine reduced the iodine concentration in milk. Though the ability of the goat to concentrate iodide in milk is greater than for the cow, the mechanisms of concentration appear to be similar.