Effect of Potassium Iodide and Thyroid Extract on Thyroid Gland of Guinea-Pig. ∗

Abstract

In a series of investigations on the compensatory hypertrophy of the thyroid gland in guinea pigs, it was found that within the normal gland there was discernible a formation of three layers which differed in (1) the size of acini, (2) the more or less solid state of the colloid, (3) the quantity of this substance and (4) the height or flatness of the epithelium lining the acini. There is usually associated with a greater hardness and a greater quantity of the colloid a greater flatness of the epithelium. 1 This suggested that the character of the epithelium lining the acini may be determined, at least in part, by the condition of the colloid, and in particular by the presence or absence of pressure exerted upon the epithelium by this substance, and by surrounding acini. There was some apparent confirmation of this view in the further observation that, not rarely, the walls separating neighboring acini may be broken through, and that such a change may be followed by the union of the colloid material of both acini. This fact also suggested a pressure effect.

It has been observed by Marine and Lenhart 2 that in certain kinds of goitre, administration of potassium iodide may cause an increase in the amount of colloid of the acini, and reduce the height of the epithelium. More recently several authors have found that in exophthalmic goitre potassium iodide may at least temporarily lead to a reduction in size of the epithelium lining the acini. On the other hand, it has been observed that under certain conditions administration of this substance may intensify the symptoms of abnormal thyroid activity, and in our series, referred to above, it was shown that contrary to current opinion, feeding of potassium iodide to guinea pigs, from which great parts of their thyroid gland had been removed, did not diminish the subsequent compensatory hypertrophy of this organ, but that, on the contrary, in our rather extensive series, it seemed definitely to increase the size of the cells, the number of mitoses, as well as the fluidity and absorption of the colloid.