This is usually a benign tumor of the pituitary gland, which is situated at the base of the brain. Pituitary tumors primarily affect older female rats. The location makes the tumor inoperable, and the compression of nearby brain tissue likely. In contrast to strokes, the onset of weakness in an expanding pituitary mass is gradual. Commonly, the forelimbs will become weak first, and the rat will have trouble holding food.
Weakness can then spread to the hindlimbs.
Pituitary tumors carry a poor prognosis, but early treatment with prednisone can temporarily relieve symptoms. In addition, there has been some evidence that antibiotics can shrink tumors, and these may be added to the treatment regimen. Perhaps the best treatment for pituitary tumors is preventive. These are hormone-driven tumors, as are mammary tumors, therefore spaying greatly reduces their incidence. Spaying rats, of course, is a controversial and risky procedure, and not all rat owners condone it.