The researchers found a way to measure the amount of iodine stored in the human thyroid gland and how much hormone it produces each day. They used a method involving radioactive iodine and thyroid-stimulating hormone to estimate the hormone stores in the gland. This technique allowed them to directly determine the specific radioactivity of the newly secreted hormone, without needing to wait for equilibration of different compartments. This method could help understand thyroid diseases better and determine the right treatment needed.