[1] His residency and fellowship at Mayo Clinic in Rochester, Minnesota, which began in 1945, was interrupted by two years of military service in Germany with the Medical Corps following the Second World War.
He developed an interest in endocrinology, the thyroid and radioactive iodine at Mayo, and in 1952 he was awarded a PhD by the University of Minnesota for research on the metabolism of thyroxine.
[3] In New York, he was an assistant professor at Cornell University Medical College and began research into radiation-induced thyroid cancer as a result of hydrogen bomb testing in the Marshall Islands.
The branch initially focused on thyroid physiology and diseases, but later expanded to encompass diabetes as well as disorders of growth hormone and the gonads.
Under Rall, the CEB hosted many visiting international scientists and had a longstanding association with the laboratory run by Nino Salvatore in Italy.