The hypothalamo pituitary axis, as the true conductor of the endocrine orchestra, is frequently involved in a large variety of pathological conditions such as acromegaly, behavioral disorders, obesity or dwarfism. It is paradoxical to note that, in spite of its importance, this system has been almost ignored by the physiologists of the late centuries. From the physiological conceptions of the physicians and philosophers of antiquity to the theories of the medieval and of the Renaissance physiologists, we will try to understand why the role of pituitary remained so long unrecognized.