Atrophy of Thymus of the Rat Resulting from Administration of Adrenocorticotropic Hormone. ∗

Abstract

Some time ago publication was made from this laboratory of the rapid atrophy of the thymus on the administration of the gonadotropic hormone in pregnant mare serum. 1 The phenomenon was not seen in males or females after castration and was tentatively referred to the increased production of sex hormones on the part of the gonad. Selye, Browne and Collip 2 have noted atrophy of the thymus following administration of progesterone. Selye, Harlow and Collip, 3 and Schacher, Browne and Selye 4 subsequently produced regression of the thymus by administration of estrogenic, as well as androgenic substances. The preparation of adrenocorticotropic and mammotropic hormones in this laboratory has resulted in their administration under a variety of conditions. It became apparent very soon that invariable prompt reduction in size and almost complete regression of the thymus occurs 5 after administration of adrenocorticotropic hormone, while mammotropic hormone does not produce the atrophy. Although adrenocorticotropic hormone in large doses causes a stunting of growth or a loss in body weight, the doses used here which were effective in reducing thymus weight were not always associated with loss of body weight.

It is now known that an increase in the production of cortin by the adrenal is provoked by adrenocorticotropic hormone,⁶ as well as a demonstrable increase in its secretion of androgenic and estrogenic substances, ^{7, 8, 9} and one may naturally inquire as to which of these adrenal functions we may attribute the above mentioned experimental thymic atrophy. The reduction of the thymus by adrenocorticotropic hormone with equal facility after double ovariectomy would appear to rule out the stimulation of the production of progesterone, or androgenic and estrogenic substances, from the ovary which adrenocorticotropic hormones could conceivably occasion.