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'''Rosalyn Yalow''' an American medical physicist (1921-2011) who developed the radioimmunoassay, a technique of extraordinary sensitivity for measuring minute quantities of biological substances. For this work she received the Nobel Prize in Physiology or Medicine in 1977, the second woman to win the prize in medicine.

== Early Life and Education ==
Rosalyn Sussman was born in 1921 in the Bronx, New York, the daughter of Jewish immigrants who ran a small stationery shop. She was determined from an early age to become a physicist, despite the scarcity of opportunities for women, and she attended Hunter College, a free public college for women, where she majored in physics and chemistry.

After graduating in 1941 she worked as a secretary to a biochemist at Columbia University, taking courses in her spare time, and in 1943 she was offered a teaching assistantship in physics at the University of Illinois, one of the few graduate programs that would admit a woman. She was the only woman among the four hundred students in her entering class.

At Illinois she met Aaron Yalow, a fellow graduate student in physics whom she married in 1943. She received her doctorate in 1945 with a thesis on the radioactivity of certain radioactive isotopes, and she returned to New York, where she sought a position that would allow her to combine research with the demands of family life.

== The Development of Radioimmunoassay ==
In 1947 Yalow joined the Veterans Administration Hospital in the Bronx, where she worked for the whole of her career and became a leading figure in the new field of nuclear medicine. She was given the task of setting up a radioisotope service, and she began to use radioactive tracers to study the behaviour of hormones and other substances in the body.

Working with the endocrinologist Solomon Berson, she developed a method for measuring insulin in the blood of diabetic patients. They used radioactive insulin and antibodies that bind to it, and they observed that the competition between labelled and unlabelled insulin for the antibody made it possible to measure the concentration of the hormone with a precision far beyond any previous technique.

The method, which they called radioimmunoassay, was announced in 1960. It used the specificity of antibodies, the sensitivity of radioactive detection and the principle of competitive binding to measure substances present in the body at concentrations of a few parts in a billion. It was, in effect, a way of using the immune system as an analytical instrument of unprecedented power.

== Applications and Medical Impact ==
Radioimmunoassay was soon applied to the measurement of a wide range of substances, including hormones, enzymes, vitamins, drugs and the molecules of viruses. It made possible the diagnosis of thyroid disease, the management of diabetes and the detection of hepatitis and other infections, and it became one of the most important techniques of clinical chemistry and medical research.

Yalow used the method to study the biology of insulin and the causes of diabetes, and she showed that maturity-onset diabetes is often associated with an abnormal form of insulin rather than with a simple deficiency. Her work on hormones and on the growth and function of the body's glands contributed to the understanding of many metabolic disorders.

The technique also transformed endocrinology and pharmacology, allowing researchers to follow the fate of drugs in the body and to measure the levels of substances that had previously been inaccessible. It became a standard part of the hospital laboratory and of the drug development process, and its principles were extended to other methods of analysis and detection.

== Partnership, Method and the Practice of Science ==
The collaboration with Berson was one of the most fruitful in medical research, producing more than two hundred papers over more than two decades. They worked side by side without hierarchy, sharing ideas and credit, and colleagues recalled their long discussions and their mutual trust. Berson died suddenly in 1972, and Yalow carried on their work alone.

Yalow's method was marked by rigorous attention to measurement and a readiness to challenge accepted ideas with carefully collected data. She insisted on the importance of quantifying the behaviour of biological systems and on understanding the underlying physics of the tools she used, and she was sceptical of conclusions that rested on incomplete evidence.

She believed that women could succeed in science if they were willing to work with determination, and she advised young women to combine ambition with a clear plan for their lives. She maintained her laboratory and her research programme into her final years, and she trained a large number of physicians and scientists who disseminated the techniques she had developed.

== Recognition and Legacy ==
Yalow received the Nobel Prize in Physiology or Medicine in 1977 for the development of the radioimmunoassay, an award made to her alone after the death of her collaborator. She was the second woman to receive the prize in medicine, and she received many other honours, including the Albert Lasker Award, the National Medal of Science and membership of the National Academy of Sciences.

Her method reached into nearly every branch of medicine and biology. It allowed the early detection of disease, the monitoring of therapy and the exploration of physiology at a scale that had been unimaginable, and it paved the way for the sensitive assays used in modern diagnostics and in the testing of blood for the presence of drugs and hormones.

She died in 2011 in the Bronx, the place where she had been born and had spent her working life. Appointed to a professorship at the Albert Einstein College of Medicine even though she had once been advised that women would never be accepted in such a role, she remained an advocate for women in science, and her story continues to be told as an example of perseverance and of the practical power of physics applied to medicine.

== See also ==
* Radioimmunoassay
* Nuclear medicine
* Solomon Berson
* Insulin

== References ==

<ref name="r1">Rosalyn S. Yalow and Solomon A. Berson, Immunoassay of Endogenous Plasma Insulin in Man, Journal of Clinical Investigation, 1960.</ref>
<ref name="r2">Eugene Straus, Rosalyn Yalow, Nobel Laureate: Her Life and Work in Medicine, Plenum Trade, 1998.</ref>
<ref name="r3">Rosalyn S. Yalow, Radioimmunoassay: A Probe for the Fine Structure of Biologic Systems, Nobel Lecture, 1977.</ref>
<ref name="r4">Ann G. Carmichael and others, Medicine: A Treasury of Art and Literature, Macmillan, 1991.</ref>

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[[Category:Science]]
[[Category:Medicine]]
[[Category:United States]]