Hypersomatotropism (veterinary)

Hypersomatotropism, in veterinary medicine, refers to a condition characterized by excessive secretion of growth hormone (GH), also known as somatotropin. This overproduction of GH leads to insulin resistance and, consequently, the development of diabetes mellitus. It is most commonly recognized in middle-aged to older cats, where it is a significant cause of acquired diabetes. While less common, it can also occur in dogs.

The primary cause of hypersomatotropism is a functional pituitary tumor (adenoma or carcinoma) that secretes excessive amounts of GH. The elevated GH levels stimulate the liver to produce insulin-like growth factor 1 (IGF-1). IGF-1 has diverse anabolic effects, contributing to tissue growth and overall body size. However, the chronically elevated levels of GH and IGF-1 interfere with insulin's ability to effectively regulate blood glucose, leading to insulin resistance and hyperglycemia.

Clinical signs in affected animals often include:

• Uncontrolled diabetes mellitus, requiring high doses of insulin.
• Weight gain, despite being diabetic.
• Increased appetite (polyphagia).
• Increased thirst (polydipsia).
• Increased urination (polyuria).
• Prognathism (elongation of the lower jaw).
• Organomegaly (enlargement of internal organs, such as the kidneys or heart).
• Increased interdental spaces.
• Respiratory stridor (in cats, due to soft tissue swelling in the pharynx and larynx).
• Arthropathy (joint disease).

Diagnosis typically involves a combination of clinical signs, persistent insulin resistance, elevated serum IGF-1 levels, and advanced imaging techniques (such as MRI or CT scan) of the pituitary gland.

Treatment options are often challenging and may include:

• Radiation therapy of the pituitary tumor.
• Hypophysectomy (surgical removal of the pituitary gland). This is a highly specialized procedure.
• Medical management with somatostatin analogs (e.g., pasireotide), which can suppress GH secretion.

The prognosis for animals with hypersomatotropism varies depending on the severity of the disease, the presence of concurrent health problems, and the chosen treatment approach. Early diagnosis and intervention can improve the quality of life and potentially extend the lifespan of affected animals.