Jacob Robbins, an NIH thyroid researcher and co-discoverer of the active form of thyroid hormone, died on May 12 in Bethesda, Md, of heart failure. He was 85 years old.

In the 1950s Robbins and colleague Joseph Rall, both then at Memorial Sloan-Kettering Cancer Center, hypothesized that levels of the thyroid hormone, thyroxine, might fluctuate in the bloodstream and found that the hormone could not be bound to any other proteins in the blood in order to be active.

"It was extremely important for understanding how to give thyroid hormone as medication and how the thyroid functions in the body," Phillip Gorden, a former director of National Institutes of Diabetes and Digestive and Kidney Diseases (NIDDK) told The Washington Post.

In subsequent work Robbins showed the effect of radioactivity on thyroid cancer, surveying survivors from Hiroshima, Marshall Island and Chernobyl. He joined the NIH in 1954 and in 1963 became the chief of the Clinical Endocrinology Branch.

Robbins published more than 250 papers, and his 1957 paper on proteins associated with the thyroid hormones has been cited more than 515 times, according to the ISI database. In 1995, the Post reported, he retired but kept an office at NIH to study the after effects of Chernobyl.