Immunosassay of endogenous plasma insulin in man.

First radioimmunoassay of a hormone, a test capable of estimating nonogram or even picogram quantities.

In 1977 Yalow received half of the Nobel Prize in Physiology or Medicine "for the development of radioimmunoassays of peptide hormones." The other half was awarded to Roger Guillemin and Andrew V. Schally "for their discoveries concerning the peptide hormone production of the brain."