Answer: Hypothalamus
Explanation:
The hypothalamus, located in the fore brain is the important part of the brain that controls the secretion of the pituitary gland. It does this by stimulating the anterior pituitary gland to secrete its hormone, ACTH (Adrenocorticotropic hormone) which in turns stimulates the adrenal cortex to release corticosteriods that helps in fluid and salt balance in the body.
Thus, professor petrol's colleague is focusing on the hypothalamus.