Acromegaly, also known as hypersomatotropism, is a rare condition caused by excessive amounts of growth hormone in the bloodstream that cause an over-exuberant growth of tissue and bone.
Dogs and cats with acromegaly tend to be “chunky,” with big heads and big paws that are out of proportion to their body. Indeed, one clue that a pet has acromegaly is if the teeth move apart (gaps between the teeth) so he has the equivalent of a gappy smile. This is because the jaw bone continues to grow, spacing the teeth apart.
The effect of this continued growth has an impact on organ function. Acromegaly is one reason my diabetic cats may be difficult to stabilize because the growth hormone interferes with the body’s ability to recognize insulin.
Again, dogs and cats with acromegaly tend to have oversized heads and paws. Sadly, this is about more than appearance because the condition may affect organ function.
Acromegaly strains the heart muscle, and heart disease leading to heart failure is a recognized complication. The continued growth of bones also strains the joints, and affected animals are more likely to suffer from arthritis.
The biggest implication of all concerns diabetic pets because the growth hormone stops body tissue from recognizing insulin, which makes regulation of blood sugar levels difficult indeed.
On a day-to-day basis, affected animals are likely to be hungry and thirsty.
They grow excess folds of skin, which tend to thicken. These folds can also develop at the back of the throat and cause noisy breathing (akin to snoring).
Long-term use of progestogen-containing medications can induce acromegaly. This is rare these days, however, because a drug commonly used 20 years ago containing progestogen has fallen out of favor (because of its many side effects).
The most common cause lies in the part of the brain responsible for secreting growth hormone. The pituitary gland at the base of the brain develops a tumor, which then secretes too much growth hormone as a result of the cancerous change.
Within the past couple of years, a blood test has been developed that measures levels of growth hormone. The sample can be taken by your veterinarian but is sent to an outside lab for analysis.
Ultimately, the diagnosis is made on an MRI scan to visualize the brain and look for a pituitary tumor (the most likely cause of this condition).
Treatment is very much a specialist procedure. In fact, there are few surgeons with the necessary training to perform this procedure.
The therapy is ablation (destroying) of the pituitary tumor, a delicate and risky procedure. A number of surgeons, however, are performing this groundbreaking procedure at university veterinary facilities, and, although unusual, it is becoming more routine.
Apart from avoidance of long-term medications that contain progestogen, there is no known prevention for acromegaly.
- “Progestins and growth hormone excess in the dog.” Selman. Acta Endocrinologica, 1: 42.
- “Growth hormone related disorders in dogs.” Campbell. Comp Cont Ed, 10(40): 477–482.
This pet health content was written by a veterinarian, Dr. Pippa Elliott, BVMS, MRCVS. It was last reviewed Oct. 1, 2015.