It would be incredibly difficult to imagine thyroidology at a time when physicians had no accurate method for measurement of the different hormones.  In fact at the time it was believed by many that a radioimmunoassay of the different thyroid hormones was impossible due the simplicity and similarity of the molecules.  It was during this period that as young physician at the Harbor UCLA Dr. Inder Chopra revolutionized thyroidology by creating the very first radioimmunoassays for virtually all of the thyroid hormones and their metabolites.  

His efforts created a tool that could for the first time explain thyroid hormone production and metabolism in the body and created a very sensitive method for monitoring the the thyroid hormones in the body.