A person with a pituitary tumor has a growth of abnormal cells in the pituitary gland within the brain. The pituitary gland produces hormones and is controlled by a part of the brain called the hypothalamus.

The tumor may cause the pituitary to reduce the production of hormones, or increase the production of hormones.

Pituitary adenomas causes abnormal levels of the following hormones:

• Steroid hormones:
• Cortisol
• Sex hormones:
• Estrogen
• Testosterone
• Growth hormone
• Prolactin:
• Stimulates milk production in the breast
• Thyroid hormones:
• Thyroxine

These tumors usually do not spread to other areas of the brain or body.