Endemic Goiter in Western New Guinea: Iodine Metabolism in Goitrous and Nongoitrous Subjects

Abstract

Studies of iodine metabolism were made in the Papuan population of Mulia (central highlands of Western New Guinea), which is affected by extremely severe endemic goiter and probably by cretinism. The inhabitants are an isolated community in an economic but not in a genetic sense. The excretion of iodine in the urine, as directly determined in a large number of subjects, was below 5 μg/day. The fecal iodine loss, calculated from studies with I¹³¹-labeled thyroxine, was of the same order. The daily iodine intake, estimated as the sum of urinary and fecal excretion, thus appeared to be less than 10 μg. Inadequate adaptation to this extreme degree of iodine deprivation was evidenced by the greatly decreased serum PBI values (averages between 1.2 and 1.9 μg/100 ml in the different groups), even though there were few clinical signs of hypothyroidism. The most striking attempts at adaptation were an extremely efficient accumulation of I¹³¹ by the thyroid in all subjects (over-all average maximum 88 % of dose) and a greatly accelerated release of I¹³¹ found only in thyroids of normal or nearly normal size. The remaining data of goitrous and nongoitrous subjects were nearly identical: they did not differ in urinary excretion of I¹²⁷ or PBI¹²⁷ or in I¹³¹ uptake. Increased thyroid size therefore did not seem to favor the adaptation to iodine deficiency. The closely related people of Tiom, a goiter-free valley in the central mountains, had normal PBI values, although their iodine excretion was only 13.6 μg/day. Allowing for fecal loss of iodine, it may be estimated that an iodine intake of approximately 20 μg/day is compatible with normal life in these people. In both localities the diet was found to be extremely poor in protein and salt.