Roger Guillemin, a pioneering figure in the field of neuroendocrinology, has passed away at age 100. Born in France in 1924, as a young physician, Guillemin became interested in finding out the role of the brain in controlling the pituitary gland. Pursuing this problem took him first to Montreal, then to Baylor College of Medicine in Houston, and finally to the Salk Institute in La Jolla, CA.

Located at the base of the brain, the pituitary is known as the master gland of the endocrine system because it controls the functions of many of the other endocrine glands. In the mid-1950s, Guillemin discovered that the pituitary required input from the hypothalamus—a structure adjacent to the pituitary—in order to release its hormones. Guilleman postulated that another hormone (which he called a releasing factor) acted upon the pituitary and stimulated it to release its own hormones. Determined to isolate this factor, Guilleman began working with a young investigator named Andrew Schally.

After several years, Schally and Guilleman severed their partnership and pursued their research separately. They made their discoveries independently, but eventually they both isolated hypothalamic peptide hormones—an achievement that earned them a 1975 Lasker Basic Medical Research Award.