Since 1908 he was an assistant lecturer in the same department and immediately after his doctorate, he took up the post of Professor of Physiology in the university's School of Veterinary Medicine.

In that year, however, the military dictatorship deprived him of his university posts, due to his liberal political ideas and Houssay was forced to re-establish his research lines and staff at a privately funded Instituto de Biología y Medicina Experimental.

This situation, reinforced by a second dismissal by the Peronist government in 1945, was prolonged until 1955 when Peron was ousted from power and Houssay was reinstated in the University of Buenos Aires, where he remained until he died.

Houssay worked in many fields of physiology, but his main contribution was experimental investigation of the role of the anterior hypophysis gland in the metabolism of carbohydrates, particularly in diabetes mellitus.

Houssay's many disciples along his years of activity became also influential themselves as they spread around the world; such as Eduardo Braun-Menéndez, and Miguel Rolando Covian, who went to become the "father" of Brazilian neurophysiology, as chairman of the Department of Physiology of the Medical Faculty of Ribeirão Preto of the University of São Paulo.

Houssay wrote with them the most influential textbook of Human Physiology in Latin America, in Spanish and Portuguese, which, since 1950 has been published in successive editions and used in almost all medical schools of the continent.