The iodine plays an important role in our well-being as it controls the growth and our metabolism. Most of the iodine that we intake from our food is stored in the thyroid gland. The thyroid gland in some people may become over-active or under-active. Both these conditions are considered to be critical. The condition of thyroid in patients are understood with the help of tracer as follows: about 10 µCi of I131 in the form of NaI is given to the patient through orange juice and the counting of the γ activity emitted is started immediately. The counting is taken for several hours and then the ratio of counts D/P (dummy/patients) are plotted as a function of time. The curve obtained is compared with the curve of the normal person and thus hypothyroidisis or hyperthyroidisis is detected.