Adult-onset Panhypopituitarism In Dogs
Adult-onset panhypopituitarism is a disease in which the pituitary gland and nearby tissues like the hypothalamus are damaged or compressed. The damage causes anterior pituitary hormones to secrete less than they should, meaning the secretion becomes insufficient or disappears altogether. This causes upsets in many other hormone-producing glands and can cause a wide array of symptoms.
Pituitary tumors that are inactive usually occur in adult dogs or senior dogs, and all breeds seem to be affected indiscriminately. Injuries, infections, and other conditions that may have lead to pituitary tissue destruction can also be a causal factor of panhypopituitarism.
Most dogs affected with this disease show signs of being uncoordinated, depressed, may collapse during exercise, and often lose weight. Sometimes a change in temperament may occur, or the dog may hide or stop responding to other people. If the condition is chronic, blindness can occur as the tumor presses on the optic nerve. Animals who have this condition tend to drink more water than usual but still appear to be dehydrated. Even housetrained dogs often begin to urinate in large volumes, sometimes indoors. Unfortunately tumors usually have to grow to quite a large size before symptoms appear or death occurs. In some cases the tumor can actually replace the hypothalamus, and smaller than average adrenal and thyroid glands may be evident.
One of the best treatments for dogs with this disease is external beam radiation therapy. This therapy works well in dogs with large pituitary tumors and is very influential in reducing tumor size. However, dogs who have extremely large tumors sometimes experience inadequate results, and prognosis for these dogs is usually quite poor.
Juvenile-onset Panhypopituitarism (Pituitary Dwarfism) In Dogs
Pituitary dwarfism, the common name for juvenile-onset panhypopituitarism, is a condition that exists when the front area of the pituitary gland doesn’t develop the right way or is impeded by a tumor. As with many hormonal conditions this can cause an upset in other hormone-producing glands, and dogs affected with the disease can present with a wide range of symptoms. The most obvious symptom of pituitary dwarfism is that it causes the animal to be smaller, or dwarfed, in size at a young age.
This disease shows up most often in German Shepherds, but it has also been detected in the Karelian Bear Dog, Miniature Pinscher, and Spitz. The disease does not seem to affect one gender more than the other.
Up until dogs reach about two months of age their size will appear normal. But, if they have pituitary dwarfism, after that age they will grow slower and will usually keep their puppy coat. Normally, primary guard hairs will develop as dogs grow older, but with this disease they do not. Hair loss on the sides of the body is common, and sometimes total hair loss will occur, except for a few tufts of hair on the legs and some on the head. These dogs also fail to grow permanent teeth, or, if they do get their permanent teeth, it will be much later than usual. The growing ends of the bones will often not close until up to four years later than they should. Male dogs with the disease will display very small penis and testes, and female dogs experience irregular heat cycles or don’t have heat cycles at all. This disease also causes low levels of cortisol and thyroid hormones and deteriorating adrenal glands due to the fact that the pituitary gland also affects the production of these hormones. Unfortunately, dogs with this disease have a shortened life expectancy.
Treatment of pituitary dwarfism is not possible, as most treatments have proven ineffective. However, it is important to start daily thyroid hormone replacement treatment as soon as any evidence of secondary hypothyroidism presents. Canine growth hormone is unavailable for therapeutic uses, but porcine or human growth hormone have been used. There are, however, large differences between human and canine growth hormone, so even if dogs create antibodies against human growth hormone it won’t do any good, rendering the treatment ineffective. Porcine growth hormone has been shown to work a little better, but it is very expensive and hard to find. Progestogens have recently been used to attempt to treat congenital hormone defects and deficiencies in dogs, and has been shown to increase body size slightly and re-grow hair in some young dogs. However, the drug also has many potential negative side effects.
If left untreated the prognosis for dogs suffering from pituitary dwarfism is very poor. Canines with this condition usually become mentally slow, lethargic, thin, and bald by just three to five years of age. These symptoms are caused by expansion of pituitary cysts and the loss of pituitary function.
Diabetes Insipidus In Dogs
While their names may sound similar, diabetes insipidus and the more common version, diabetes mellitus, are not related. In fact, diabetes insipidus doesn’t involve insulin or the metabolizing of sugar at all.
Problems with antidiuretic hormone or vasopressin cause diabetes insipidus. Vasopressin, the antidiuretic hormone, controls body fluids and helps to ensure that the levels remain balanced. If the pituitary gland doesn’t produce enough vasopressin it results in central diabetes insipidus, and if the hormone is produced normally but the kidneys don’t respond to it as they should it’s called nephrogenic diabetes insipidus.
Dogs with this condition often drink excessive amounts of water and urinate frequently and in large volumes, as well. Normally the urine is abnormally dilute, even if the dog doesn’t drink water, which is highly unusual.