Pituitary tumors can produce different hormones, usually regulated by specific factors. Some tumors can make multiple hormones, like growth hormone and prolactin. It's rare for a tumor to have cells that produce corticotroph, prolactin, and growth hormone at the same time. A recent case study found a pituitary tumor with these three types of cells. This type of tumor is not common, and researchers are still trying to understand how and why it happens.