Effects of Combined Administration of Extracts of Anterior Lobe of Pituitary and of Potassium Iodide on Thyroid Gland

Abstract

In former investigations from this laboratory Loeb, 1 Gray 2 and Rabinovitch 3 have shown that potassium iodide may exert, a stimulating effect on the thyroid gland of the guinea pig. It does not prevent compensatory hypertrophy, but may modify its character; in the normal gland it may increase the mitotic activity as much as 40-60 times, and quite commonly increases it 20 times. Furthermore, it produces a slight increase in the size of the acinus cells and a slight softening of the colloid and a very marked increase in the number of phagocytes in the colloid. Loeb 4 has shown that oral administration of anterior pituitary substance (Armour & Co.) prevents compensatory hypertrophy of the thyroid gland and McCordock 5 has shown that it prevents the hyperplasia caused by potassium iodide. However, if instead of oral administration of anterior pituitary we give daily subcutaneous injections of either acid or alkaline extracts of anterior pituitary, no inhibition of the thyroid gland results, but, on the contrary, a very pronounced stimulation (Loeb and Bassett 6 ). Hyperplasia and hypertrophy of the acinar epithelium, liquefaction and absorption of the colloid proceed very rapidly. After 7 daily injections of such extracts extreme changes are found in the gland resembling in many respects those obtained in typical cases of Graves disease.

We have then in potassium iodide and in acid or alkaline extract of anterior pituitary gland 2 substances which stimulate the thyroid gland of the guinea pig and which produce a very pronounced cell proliferation in the epithelium of the acini. They differ, especially, in that the hypertrophy and softening of the colloid caused by KI is very slight as compared with the pronounced effects of anterior pituitary extracts and secondly, in that, under the influence of anterior pituitary extract, the colloid is rapidly absorbed from the acini, whereas under the influence of KI it is only slightly softened and largely retained in the acini.