I. INTRODUCTION
The endocrine glands undoubtedly play an important rôle in controlling metabolic processes. This field fascinatingly invites research study, both on account of its high scientific interest and its clinical importance. For some time past we have been investigating the influence of the thyroid gland on metabolism. The problems investigated have comprehended the relation of the thyroid to (1) carbohydrate metabolism, (2) protein metabolism and (3) thyroid therapy.In the present article the influence of the thyroid on certain aspects of protein metabolism are considered. Although it has been known for a long time that the administration of thyroid preparations stimulates protein catabolism, and conversely that the abolition of thyroid function diminishes tissue breakdown, still our knowledge of the influence of the thyroid on specific nitrogen metabolites such as ammonia, creatinin and the purins has remained rudimentary. Better information is here very desirable, since if one could, for example,