Effect of low and high ambient temperatures on metabolism of radioiodine by the lactating goat.

Two lactating goats given an oral dose of iodine-125 excreted 16.8, 52.5, and 9.8% of the dose into the milk, urine, and feces when the ambient temperature was 33 C. The thyroids contained about .7% of the oral dose. At 5 C only 2.6% of the radioiodine was in the milk, but 71.2% was in the urine, 18.1% in the feces, and about 10% in the thyroid. The reduced competition by the thyroid plus enhanced transfer of radioiodine from blood to milk at 33 C was responsible for the large transfer of radioiodine into milk at 33 C.