Goiter-inducing effects of milk. 3. Changes in thyroid weight. Study of thyroid function using I-131

Abstract

For one year two groups of female Wistar rats were fed on milk. The experimental group (group A) was fed on milk from a goitrous area and the control group (group B) on milk from a farm in the South of Pamplona, Spain.

In eight different phases of the experiment throughout one year thyroid -weight, thyroid I131 uptake of I'” and PBI131, I131 elimination in uriníƒe and faeces and hormo­ nal biosynthesis were studied.

In a phase of the experiment the subjets (fed on milk) were bred with males (kept on a regular diet). The rats born (groups At and Bn born of rats the groups A and B, respectively) were also fed on milk (rats of group A, on goiterous milk and rats of group Bj on regular farm milk), when the rats of groups Al and B, were one year oíd thyroid weight and thyroid uptake of I131 and PBI131 were studied in them.

Goiter was not found in rats of the first generation (groups A and B); however, the animáis of the second generation (groups Aj and BJ showed a noticeable increase in thyroid size, this increase being significantly higher in rats of group A, (P 0.01-0.001) than in those of group B, (P 0.05-0.02).

The study of radioactivity distribution (I131) by means of chromatography of thyroid hydrolised showed an inversión of the ratio MIT/DIT, by an increase in the amount of MIT.

It is concluded that the increase in thyroid size in rats of group At is probably due to the goiterous milk they were fed on. Among the possible goiter-inducing factors of this milk the one of highest inníƒuence is probably thiocianate; nevertheless, other pos­ sible factors not yet investigated cannot be discarded, these hypothetical factors perhaps accounting for the weak effect found in rats fed on regular farm milk.