Acromegaly is a type of musculoskeletal disorder marked by progressive enlargement of the head, face, hands, and feet due to excessive secretion of growth hormone (GH) somatotropin. Chronic overproduction of growth hormone in man and cat is most often caused by a GH-producing tumor of the pituitary gland. In dogs the usual cause is quite different and the disorder is reversible. Signs include gait abnormalities consisting of chronic progressive stiffness and rigidity. Other symptoms of this musculoskeletal disease are increased appetite associated with weight gain, excess urination (polyuria) and increased thirst (polydipsia), excessive panting, progressive thickening of the skin, prominent skin folds, noisy breathing and enlargement of the tongue. A definitive diagnosis requires measurement of increased plasma growth hormone or insulin-like growth factor 1 (IGF-1) concentrations in suspected cases.
Acromegaly is encountered in intact female dogs that were treated with progestagens to prevent estrus and in dogs during diestrus, or period of sexual inactivity. Progestagen withdrawal and/or ovariohysterectomy will result in a reduction of plasma GH and GH-dependent insulin-like growth factor concentrations and appreciable clinical improvement. Definitive diagnosis can be difficult because of the gradual disease onset, subtle clinical signs, unavailability of relevant laboratory tests, and client financial investment. The most significant clinical finding of acromegaly is the presence of insulin-resistant diabetes mellitus. Diagnosis is currently based upon brain imaging and measurement of serum GH and/or insulin-like growth factor-1 concentrations. Definitive treatment in cat is not well described, but radiation therapy appears promising.
Saint Bernards are believed to be predisposed to acromegaly due to high frequency of abnormalities in the anterior pituitary.