Yalow, Rosalyn Sussman (1921– )

US physicist who was awarded a Nobel Prize for Physiology or Medicine in 1977 for the development of radioimmunoassay (RIA) techniques by which minute quantities of hormone may be detected. It can be used to discover a range of hormones produced in the hypothalamic region of the brain.

Yalow was born in New York and studied at Hunter College and at the University of Illinois. In the 1940s she started working in the Radioisotope Unit of the Veterans Administration Hospital in the Bronx, New York, with a medical doctor, Sol Berson. When he died in 1972, Yalow was appointed director of the laboratory.

To measure the concentration of a natural hormone, a solution containing a known amount of the radioisotope-labelled form of the hormone and its antibody is prepared. When a solution containing the natural hormone is added to the first solution, some of the labelled hormone is displaced from the hormone–antibody complex. The fraction of labelled hormone displaced is proportional to the amount of the natural hormone (which is unknown).