A review of 202 publications. Experimental and clinical studies have on the whole supported the common attribution of certain symptoms (as in cretinism and in myxedema), to hypofunctioning of the thyroid, but have given less support to the attribution of others (as in exophthalmic goiter) to hyperfunctioning. Many studies have been made on the relations of the thyroid to growth, to metabolism, to sex, and to learning.