The adrenal glands, located beside each kidney are integral both to life-sustaining metabolic activities and to the body's fight-or-flight response. Adrenal hormones are involved in:
- protein, fat and carbohydrate metabolism
- water metabolism
- blood pressure regulation
- sodium and potassium concentration
- Additionally, the adrenals produce a little sex hormone.
Cortisone, Cortisol And Corticosteroids
Broadly speaking, the adrenals produce two types of corticosteroids, sometimes also called cortisone or cortisol. Mineralocorticoids are responsible for sodium and potassium concentration and water balance. Glucocorticoids are responsible for protein, fat and carbohydrate metabolism. Glucocorticoids also reduce inflammation and suppress the immune system. When we put your pet on "cortisone" we dispense a synthetic corticosteroid such as prednisone, prednisolone or methylprednisolone. These, especially the latter have little mineralocorticoid activity.
Many pet owners are concerned about their pets being given "cortisone".
In excess corticosteroids cause all the signs of Cushing's Disease which is described in the following paragraph. Your concern is valid when corticosteroids are used needlessly or excessively but unwarranted when these drugs are used appropriately and therapeutically. Unlike most other drugs, corticosteroids such as prednisolone are as close to as natural as medicine offers. This is what makes them so effective. They are most effective in two situations, when the immune system runs amok and needs suppression and when the body is in clinical shock. In both circumstances corticosteroids are life-savers. We have probably saved more lives using corticosteroids than using antibiotics. Don't be afraid of side effects of corticosteroids when these drugs are necessary. Talk to us about any worries you might have.
Overactive Adrenal Gland - Hyperadrenocorticism - Cushing's Disease/Syndrome
Cushing's disease, named after the Boston doctor who first described it in humans, is an overactivity of the cortisol-producing adrenal gland (hyperadrenocorticism). It is most commonly caused (85 percent) by excess pituitary production of adrencorticotropic hormone (ACTH). In dogs about half of all affected individuals have small pituitary gland tumours. It can also be caused (15 percent) by a tumour in the adrenal gland itself. Primary Cushings is rare in cats. If it is caused by excess medical use of corticosteroids, it is called "iatrogenic Cushing's Disease. Typically, an affected pet drinks and urinates excessively and is constantly hungry. It develops a pot-bellied appearance. Hair falls from the body, although not from the head or legs, and does not regrow if it is shaved. Pets pant more are weaker and more lethargic. Skin infection (pyoderma) is not uncommon.
Diagnosis And Treatment
On blood test there are changes to white blood cells and increased liver enzyme activity. There may be excess sugar in blood. X-rays or ultrasound show liver and adrenal gland enlargement in most affected pets. In males the testicles are often small. A definitive diagnosis is made by monitoring the adrenal glands' cortisol response to stimulating and/or suppressing them with hormonal drugs. This is done to determine whether the source of the disease is in the pituitary or the adrenal gland.
Pets with pituitary-associated Cushing's are treated with a drug that suppresses adrenal overactivity. Iatrogenic Cushing's disease usually spontaneously resolves when the dose of corticosteroid is gradually reduced.
Underactive Adrenal Gland - Hypoadrenocorticism - Addison's Disease/Syndrome
Addison's Disease, named after a 19th century English physician, is an underactive adrenal gland (hypoadrenocorticism). This is a more difficult to diagnose condition usually seen in female dogs between two and seven years old. It may be an autoimmune disorder. Typically, the illness comes and goes, making it difficult to diagnose. We have seen it most frequently in Leonbergers. The common signs are loss of appetite, lethargy and depression. Pets lose weight and are intermittently weak.
Diagnosis And Treatment
Changes in serum electrolytes (low sodium, low chloride, high potassium) are common. A low response to an ACTH stimulation test is diagnostic. Pets are treated with both mineralcorticoid and glucocorticoid supplements. A combination of prednisolone (low mineralcorticoid activity) and fludrocortisone (high mineralcorticoid activity) is common.