What was the first hormone discovered?
Secretin
It has been suggested that abnormalities in such secretin release could explain the abnormalities underlying type D syndrome of inappropriate antidiuretic hormone hypersecretion (SIADH).[7] In these individuals, vasopressin release and response are normal, although abnormal renal expression, translocation of aquaporin 2, or both are found.[7] It has been suggested that "Secretin as a neurosecretory hormone from the posterior pituitary, therefore, could be the long-sought vasopressin independent mechanism to solve the riddle that has puzzled clinicians and physiologists for decades."[7]