Pituitary Adenomas

Pituitary adenomas are very common in rats, especially females, and incidence is increased by ad lib feeding of high-calorie diets. Clinically, rats may have head tilt and depression or die suddenly. Grossly, tumors vary in size. They are soft, have well-defined margins, and hemorrhage may be present. They frequently compress adjacent brain tissue, which may lead to hydrocephalus. Pituitary tumors commonly secrete prolactin. 1

Clinical Signs
May see any combination of the following:
Mechanical disturbances

  • Gradual weakness and lack of coordination (often more noticeable in the forelimbs).
  • Stiffness or inability to flex forelimbs that gradually progresses to the hind limbs as the tumor continues to grow.
  • One eye protruding more than the other. This can be due to asymmetrical growth of the tumor pressing on structures behind the eye, and is referred to as exophthalmia.
  • Unequal pupil size in one eye compared to the other (may appear as blown/dilated pupil due to pressure or bleeding behind the eye).
  • Difficulty holding food when eating.
  • Circling, head tilt, seizures, hydrocephalus and sudden death.
  • Head pressing/Head bumping. This sign may be present when there is increased intracranial pressure (rat may bump head up when petted, or extend head pressing against a fixed surface).

Hormonal disturbances

  • Lactation (ejection of milk) in an aged non-pregnant female
  • Decreased fertility
  • Thinning skin
  • Weight loss
  • Excessive thirst (need to refill water bottles more than usual)
  • Excessive excretion of very dilute urine
  • Dehydration

Recommended treatment is geared for comfort and the reduction of clinical signs.

Prednisone, prednisolone, or oral dexamethasone, and a broad-spectrum antibiotic (e.g. Baytril) can be given to help reduce tissue swelling temporarily that accompanies the tumor.

Euthanasia should be considered if the rat’s clinical signs preclude comfort and quality of life. 2


  1. Merck Vetrinary Manual
  2. Health Guide: Pituitary Tumor

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