Why does acromegaly cause vision loss and headache?

These symptoms are caused not by the acromegaly itself, but by the pituitary tumor. These tumors are almost always benign, meaning that they do not spread to other parts of the body. However, they can cause problems as they grow. They press on surrounding areas of the brain, blood vessels, and nerves. For example, they can press on the optic nerve, causing vision problems. Pressure on other nerves can cause headache. The size of the tumor determines whether these symptoms occur and how severe they are.
 
Pituitary tumors also can damage the gland itself, disrupting hormone production. The resulting hormone imbalances are responsible for symptoms such as impotence, low sex drive, and changes in the menstrual cycle.