Argentine physiologist and corecipient, with Carl and Gerty Cori (Cori, Carl; and Cori, Gerty), of the 1947 Nobel Prize for Physiology or Medicine. He was noted for discovering how pituitary hormones regulate the amount of blood sugar (glucose) in animals.

Working with dogs that had been rendered diabetic (diabetes mellitus) by excision of the pancreas (1924–37), Houssay found that removal of the adenohypophysis (the anterior, or frontal, lobe of the pituitary body, located beneath the brain) greatly relieved the symptoms of the disease and made the animal unusually sensitive to insulin. He demonstrated that injection of pituitary extracts into normal animals induces diabetes by increasing the amount of sugar in the blood, indicating that the secretions of the gland oppose the action of insulin.

Appointed a professor of physiology in 1910 and the director of the physiological institute at the University of Buenos Aires in 1919, Houssay was one of 150 Argentine educators dismissed from their posts by the 1943 military coup of General Juan Perón. Although he was reinstated in 1945, he was asked to submit his resignation a year later. He founded (1944) and directed (from 1946) the privately funded Institute of Biology and Experimental Medicine in Buenos Aires, a leading physiological research centre. His best-known book is Human Physiology (1951).