The pituitary gland is a pea-sized gland situated at the base of the brain (see diagram below). It is responsible for releasing a number of hormones involved in regulating the biochemistry of many parts of the body. The front (the anterior) of the pituitary gland is involved in controlling the breasts, adrenals, thyroid, ovaries and testes, which themselves release other controlling hormones. The back (or posterior) of the pituitary controls the kidneys.
One of the hormones released by the anterior pituitary is adrenocorticotrophic hormone (ACTH), which has been used to manage relapses in multiple sclerosis. Nowadays, synthetically manufactured glucocorticoid hormones such as prednisolone and methylprednisolone are preferred to ACTH because of their increased potency and more benign side-effect profile.
Pituitary Gland links:
Anatomy of the Brain - Pituitary Gland
Functional Anatomy of the Hypothalamus and Pituitary Gland