The pituitary gland is comprised of three, more or less, separate endocrine glands that produce a relatively large number of hormonally-active substances. These include six well characterized hormones secreted from the anterior lobe of the gland: ACTH, discussed above, the two gonadotropins, thyroid stimulating hormone, growth hormone and prolactin. In addition, the anterior lobe secretes lipotropin and pro-opio-melanocortin, precursors of ACTH, opioid peptides and melanocyte-stimulating hormone (MSH).

The intermediate lobe, practically indistinguishable from the anterior lobe in humans, and formed of scattered cells in the adult, secretes MSH, lipotropin, opioid peptides and the large precursor, pro-opio-melanocortin.

The posterior lobe secretes two peptides, vasopressin (sometimes called antidiuretic hormone, ADH) and oxytocin.