Endocrine glands produce hormones that control all kinds of activities in the body at the cellular level. These glands are found throughout the body, from the brain where the hormones dopamine and oxytocin are made, to the thyroid gland in the neck, to the adrenal glands in the abdomen, which produce stress-managing corticoids, to the insulin producing pancreas, to the sex organs, which produce androgens and estrogens.
That sounds like a lot of glands, but it’s not even the half of it! Our endocrine system is imperative to life, and while you may not notice if your pet’s is working correctly, you’ll be hard pressed to miss when it’s not. When the endocrine system goes awry, your pet has what’s called an endocrinopathy. There are five common endocrinopathies seen in dogs and cats, and I’ll cover them each briefly now.
Diabetes mellitus. We recently discussed diabetes in the Diabetes Primer blog, but here’s a very, very short refresher. Diabetes occurs due to a lack of insulin. This lack of insulin can be absolute (meaning none is produced) or relative (meaning not enough is produced). When there is a lack of insulin, the blood sugar surges because glucose (food for the cell) cannot get into the cell without its carrier, insulin. Both dogs and cats can get diabetes, though dogs generally get insulin dependent diabetes while cats generally get non-insulin dependent diabetes (usually associated with obesity). Clinical signs include increased water intake, increased urination, increased appetite, and weight loss.
Hyperthyroidism. This condition occurs in middle aged to older cats. While it is possible for a dog to develop hyperthyroidism, it is rare. Hyperthyroidism occurs when there is an increased production of thyroid hormone, which leads to a high metabolic state. Hyperthyroidism in cats is usually due to benign proliferation of the thyroid gland, while in dogs, neoplasia is usually to blame. Due to an increased metabolic state, affected animals will lose weight despite a voracious appetite.
Hypothyroidism. The condition occurs in older dogs and very rarely in cats. Hypothyroidism refers to the condition when there is a decreased amount of thyroid hormone. The majority of canine cases are due to a benign destruction of thyroid cells. As you might imagine, too little thyroid hormone would lead to a decreased metabolic state, so unlike pets with hyperthyroidism, these dogs typically gain weight despite a steady diet. Skin conditions may also occur. Once diagnosed, dogs can be treated by supplementing their thyroid hormones daily.
Hyperadrenocorticism (Cushing’s Disease). Hyperadrenocorticism occurs in dogs (and rarely cats) when the adrenal glands produce too much of a hormone called glucocorticoid. Glucocorticoid is an important hormone that helps the body deal with stress, but excess glucocorticoid can cause illness. Hyperadrenocorticism most frequently occurs because a pituitary tumor tells the adrenal gland to make excess hormone, but in about 10% of cases, an adrenal tumor is to blame. Clinical signs include increased thirst, increased urination, increased appetite, pot-bellied appearance, hair loss, and panting.
Hypoadrenocorticism (Addison’s disease). Hypoadrenocorticism occurs in dogs (and rarely cats) when the adrenal glands do not produce enough glucocorticoids, mineralocorticoids, or both. These hormones are key in dealing with day to day stress as well as balancing important electrolytes. Clinical signs can be intermittent and include vomiting and diarrhea, weakness, slow heart rate, and collapse. Diagnosis can be a little bit tricky, but once diagnosed, your pet will be treated with hormone supplements. Particular care should be taken during stressful situation, such as boarding.
These short synopses don’t even come close to scratching the surface of these frustrating endocrinopathies. If you’re interested in more detailed information, revisit our blog series called The Gland Scheme of Things.