THE EFFECT OF THYREOTROPIC HORMONE COMBINED WITH SMALL AMOUNTS OF IODINE UPON THE FUNCTION OF THE THYROID GLAND

Abstract

The administration of I to rats and guinea pigs, when given at certain levels, evidently prevents the release of hormone from the thyroid gland by the thyreotropic hormone without preventing the latter''s effect upon the cellular proliferation of the gland. Hypophysectomized rats fed a diet containing 35 [gamma] of I per 100 g., showed hyperplasia of the thyroid following inj. of thyreotropic hormone, while the O consumption remained unchanged from its low level of 35% minus. Normal prepubertal guinea pigs given thyreotropic hormone show a rise in O consumption and hyperplasia of the thyroid; if KI in doses of 100 [gamma] is given in conjunction with the thyreotropic hormone, no rise occurs in the O consumption, although the thyroid gland becomes markedly hyperplastic. The findings lend support to the hypothesis of Salter and Lerman that "the therapeutic effect of I in Graves disease is a mass-law phenomenon which favors the synthesis and deposition of thyroid hormone rather than its release." Furthermore, the importance of controlling the I intake of animals used for assaying thyreotropic hormone, if the measurement of O consumption is used as the index of thyreotropic activity, is emphasized.