Iodine in Blood and Thyroid of Man and Small Animals

IN STUDIES of iodine metabolism, particularly those involving the blood and the thyroid, it is becoming important to work with small samples. This is especially true in observations on small animals; but in the clinic, e.g., in pediatric studies, it is also essential that blood “hormonal” iodine (Salter, 1940) be determined without drawing too much human blood. This paper describes a method which will give duplicate analyses on 2 cc. of serum, and is adapted to standard photoelectric colorimeters such as are available in many laboratories at the present time. It is now well established that human thyroid function can be easured satisfactorily by serum iodine analysis, even when the serum is transmitted long distances in simple containers (Salter, Bassett and Sappington, 1941; Riggs, Gildea, Man and Peters, 1941). Normally the concentration of the “hormonal” iodine is approximately 5 micrograms per cent, or 0.05 micrograms per cc. in man.