That a relation exists between the activity of the thyroid gland and the metabolism of iodine is undeniable. The thyroid hormone has a high iodine content. It is now established that iodine is a constant constituent of human blood. There is also a constant daily excretion of iodine in the urine. The level of the blood iodine varies, likewise the amount lost daily in the urine. There is a pregnant significance to these newer facts as applied to the problem of disease of the thyroid.
The nature of this relationship between goiter and iodine has been further clarified during the past decade. A part of this has resulted from studies made on the effects of iodinization. More has been learned subsequent to the development and application of more accurate micromethods for the determination of minute amounts of iodine.
After extensive investigation it has become apparent that the level of the