Computer Simulation of Iodine Metabolism by Mammals

A digital computer simulation of iodine metabolism including thyroid function has been developed and applied to lactating and nonlactating cattle and sheep. The simulation fits the published data well. It was found that the usually measured parameters of thyroid function are not affected by lactation in cattle. In species such as sheep that excrete milk containing relatively high concentrations of iodine, lactation has a marked effect on the usually measured parameters of thyroid function. These results may explain some of the published discrepancies concerning the relation of thyroid function and lactation. A computer simulation of the metabolism of fallout iodine-131 by cattle was also made. It agrees well with the data collected. The simulation was applied to various situations that might modify iodine excretion in milk. Change of the cow to uncontaminated (stored) feed after a release of fission products would markedly reduce the milk iodine-131 concentration. The administration of agents to block thyroid hormone synthesis would reduce milk iodine-131. The blocking of the uptake of iodide by the thyroid gland would increase excretion of iodide, including its excretion in milk.