Panhypopituitarism in Dogs

The pituitary gland (at the base of the brain) is one of the most important parts of the endocrine system because it regulates the hormones produced in other important glands all over the body. Some of these hormones include the antidiuretic hormones, growth hormones, adrenocorticotropic hormone (ACTH), and the thyroid stimulating hormone (TSH). If the pituitary gland is damaged or unable to function correctly, it affects almost all other functions of the body.

Adult onset panhypopituitarism can occur in any breed due to injury, tumors, or infections but juvenile onset panhypopituitarism is more common in certain breeds such as the German Shepherd, Carnelian/Karelian Bear dog, Wolf Dog, Basset Hound, Corgi, Dachshund, Spitz, and Weimaraner. However, this condition may also be caused by cysts, infection, or a tumor. More serious complications of the deficiency of hormones include kidney failure due to underdeveloped kidneys, sterility, diabetes insipidus, Addison’s disease, hypothyroidism, blindness, Cushing’s disease, and mental retardation.

Panhypopituitarism is a pituitary gland disease that causes damage to the tissues nearby such as the hypothalamus. The compression and damage of these tissues causes anterior pituitary hormones to be decreased or to disappear completely. Because of this, your dog’s other glands do not work properly and it affects the hormones in the rest of the body. This can create symptoms such as incoordination, depression, and collapse. There are two types of panhypopituitarism, which are adult onset panhypopituitarism and juvenile onset panhypopituitarism (pituitary dwarfism). Without treatment, juvenile onset panhypopituitarism is fatal. Dogs with this condition usually live to about three to five years old at the most unless treated right away.

The symptoms of adult onset and juvenile onset panhypopituitarism are different. Some of the most often reported symptoms of each include:

Adult Onset Panhypopituitarism

• Weight loss
• Clumsiness
• Depression and lethargy
• Collapse during exercise
• Blindness
• Abnormal behavior
• Excessive thirst
• Frequent urination

Juvenile Onset Panhypopituitarism (Pituitary Dwarfism)

• Smaller than average size (short legs, bulging eyes, short jaw, and a long body)
• Hair loss on sides
• No permanent teeth
• Small penis and testicles (male)
• Irregular or no heat cycles (females)
• Lethargy
• Mental deterioration
• Extreme weight loss
• Death

Types

• Adult onset panhypopituitarism is most often due to a tumor or other damage to the pituitary gland that is most often seen in dogs over six years old
• Juvenile onset panhypopituitarism (pituitary dwarfism) is the lack of development of the front part of the pituitary gland

The causes of panhypopituitarism depend on which type your dog has.

Adult Onset Panhypopituitarism

• Destruction of pituitary tissue
• Infection
• Tumor
• Parasites
• Toxemia
• Inflammation from other traumatic injury

Juvenile Onset Panhypopituitarism (Pituitary Dwarfism)

• Genetics (German Shepherd, Carnelian/Karelian Bear dog, Wolf Dog, Basset Hound, Corgi, Dachshund, Spitz, and Weimaraner)
• Tumor
• Infection
• Cysts

The veterinarian will need to perform a comprehensive physical assessment of your dog before running any laboratory and diagnostic tests. Depending on the age and breed of your dog, the veterinary care provider will determine whether to suspect adult onset panhypopituitarism or juvenile onset panhypopituitarism (pituitary dwarfism). The symptoms and size of your dog can also help your veterinarian figure out which type of panhypopituitarism your dog has. After doing the physical assessment, the veterinarian will get some blood and urine to test for hormone imbalances and other disorders.

Other tests necessary to diagnose panhypopituitarism include plasma insulin-like growth factor-1 concentration and a growth hormone stimulation test to check the growth hormone levels. In addition, your veterinarian may measure your dog’s insulin growth factors, prolactin, follicle stimulating hormones, and thyroid stimulating hormones. An MRI, x-rays, and a CT scan may be needed as well.

To treat panhypopituitarism, the veterinarian will need to replenish your dog’s hormones. There are no canine growth hormones available yet so the only choices include thyroid hormones, progestin, and porcine growth hormones. Surgery is another option if your dog has a tumor or cyst that can be removed.

Thyroid Hormones

Some success has been found with synthetic levothyroxine replenishments. Unfortunately, absorption and metabolism varies with each dog and has to be carefully monitored.

Progestin Replenishment

Progestin replenishment with proligestone or medroxyprogesterone acetate (MPA) steroids are effective in stimulating the production of growth hormones from the mammary duct cells. This treatment is usually given every few weeks for about six months. The side effects include diabetes mellitus and allergic reactions.

Porcine Growth Hormones

Because there are no available canine growth hormones, veterinarians have been using pig (porcine) growth hormones with some success. However, it is very expensive and not very consistent.

Surgical Removal

Often, tumors and cysts are too close to the thyroid to be risked. However, your veterinarian may recommend surgical removal of a cyst or tumor if it is operable.

If your dog is not treated, her quality of life will be poor and she will not live very long. In fact, without treatment, the average age of mortality is about four years. With treatment, your dog will have a longer and better quality of life although the treatments can be expensive.