Light micrograph of a section through a human pituitary gland tumour. These tumours are abnormal growths that develop in the pituitary gland and are often considered as being brain tumours, although most are benign and treatable. Some of these tumours result in too much of the hormones that regulate important functions of the body. It is also known that other tumours can cause the pituitary gland to produce lower levels of hormones. Symptoms include headaches, vision problems and muscle wasting.