Adrenal Gland Tumors
Definition of Adrenal Tumors
An adrenal tumor is any benign or malignant mass on one or both of the adrenal glands. The tumor can be functional, which means that it stimulates unregulated secretion of one or more adrenal hormones, or nonfunctional, which means that it does not cause abnormally high levels of adrenal hormones to enter circulation.
To understand the potential ramifications of adrenal tumors, it is important to have an understanding of what the adrenal glands are, and what they do when working normally. The adrenal glands are tiny, paired structures located in the abdomen, just above each kidney. They are located near the part of the kidneys that is closest to the dog’s head. The adrenal glands make, release and regulate a number of important hormones. The outer part of the adrenals, called the adrenal cortex, produces corticosteroid hormones, including mineralocorticoids, glucocorticoids and the adrenal sex hormones progesterone, estrogen and androgens.
Mineralocorticoids, the most potent of which is aldosterone, play a key role in regulating the levels of sodium, potassium and other essential electrolytes in the blood. They are essential to maintenance of adequate internal fluid volume, normal cardiac output and proper blood pressure.
Glucocorticoids, the most important of which is cortisol, are critical to regulating metabolism of carbohydrates, proteins and fats, which makes them important for maintenance of proper blood sugar levels. They also are intimately involved with managing inflammatory reactions and suppressing the immune system. Glucocorticoids’ immunosuppressive traits help heal wounds and fight infection.
The innermost part of the adrenal glands, called the adrenal medulla, secretes epinephrine (adrenaline) and norepinephrine (noradrenaline). Both of these hormones increase heart rate and blood pressure, in addition to performing other functions.
Production and release of adrenal hormones are regulated by the pituitary gland, which is located deep inside of the brain. The pituitary gland produces adrenocorticotropic hormone (ACTH). In healthy dogs, ACTH is released from the pituitary gland when circulating levels of corticosteroids are low. ACTH stimulates the adrenal glands to produce and release more adrenal hormones. When blood levels of corticosteroids are normal, the pituitary gland stops secreting ACTH, which “turns off” the adrenal glands’ secretion of steroids.
As with other types of cancer, the causes of adrenal gland tumors are not well understood. In companion dogs, adrenal tumors are split fairly equally between adenomas, which are benign or non-malignant masses, and adenocarcinomas, which are malignant.
A malignant tumor is one that tends to progressively worsen with time and, if not treated or removed, usually will result in death of the affected animal. Malignant masses typically are highly invasive, meaning nearby tissue is
If an adrenal gland tumor is not functional, that is, it is not causing the adrenal gland to secrete abnormally large amounts of corticosteroid hormones, the affected dog usually will have no symptoms of discomfort or disease. The mass will simply be lingering on or inside of the adrenal gland, without causing any perceptible consequences. However, when the tumor is functional, meaning it does cause the affected adrenal gland to secrete abnormally large amounts of
Adrenal cancer is a mystery to most people. However, with the tools of modern veterinary medicine, it can be diagnosed and treated, or at least managed.Most veterinarians presented with a dog showing signs consistent with excess secretion of one or more of the adrenal steroid hormones will initially conduct routine blood work (a complete blood count and serum biochemistry panel) and a urinalysis. The results of these tests may suggest an adrenal gland disorder, if
As with most cancers, the goals of treating adrenal gland cancer are to remove the primary neoplastic tissue, remove or destroy any sites of metastasis, relieve any discomfort suffered by the patient and restore or prolong a good quality of life.Dogs with adrenal cancer may need to be stabilized medically before they can safely be taken to surgery for attempted removal of the affected gland. Pre-surgical medical management may include administration of certain drugs