Endocrinology

Normal neural stimulation of the hypothalamus produces corticotropin-releasing hormone (CRH). Corticotropin-releasing hormone stimulates the release of adrenocorticotropic hormone (ACTH) from the anterior pituitary. ACTH exerts its effects on the adrenal cortex and stimulates the zona fasiculata to release cortisol, the zona reticularis to release androgens and the zona glomerulosa to release mineralocorticoids, but the primary effect of ACTH is on cortisol release.

There have been several new findings in canine and feline endocrinology. We will highlight those that are useful and applicable to clinical practice. New diagnostic protocols and treatments will be discussed where appropriate.

Insulinomas are tumors that arise from the beta cells of the pancreatic islets and secrete excessive amounts of insulin, resulting in hypo?glycemia. The secretion of insulin is usually episodic, as are the resulting clinical signs. Insulinomas in dogs are typically malignant and almost always metastasize; even those appearing benign on histo?pathological evaluation. Insulinomas are rare in dogs.

Possible mechanisms of hypercalcemia.

Albumin is the major determinant of oncotic or colloidal osmotic pressure, the force that holds fluids within the vascular compartment. Most of the important osmotically-active particles in the bloodstream (such as sodium, urea and glucose) are relatively small, and pass freely between the vascular and interstitial compartments, the body's two major extracellular fluid compartments.

Hyperthyroidism is the most common endocrine disorder in cats. This disorder has been noted with increased frequency since the late 1970's. It also appears to be more prevalent in certain geographic locations.

Hyperadrenocorticism can be pituitary-dependent (PDH), secondary to cortisol-secreting adrenocortical neoplasia, or iatrogenic. Spontaneous hyperadrenocorticism is primarily a disease of middle-aged to older dogs.

Diabetes mellitus can be a very frustrating disease to deal with. The typical diabetic animal referred to a specialist in internal medicine is invariably difficult to control, insulin resistant, prone to ketoacidosis and/or hypoglycemia, and usually has concurrent diseases that complicate therapy.

The four parathyroid glands, through secretion of parathyroid hormone (PTH), regulate serum calcium concentrations and bone metabolism. The concentration of serum ionized calcium is normally maintained within narrow limits by action of the PTH on bone resorption, renal calcium excretion and metabolism of Vitamin D.

Feline hyperthyroidism is the most common endocrine disorder of older cats. Thyroid hormone excess effects multiple organ systems and the associated clinical signs range in severity from mild to severe and are quite variable from cat to cat. As a result of the increased incidence of the disease, the increased index of suspicion among practicing veterinarians and the increased screening of geriatric cats for hyperthyroidism, the average hyperthyroid cat is now evaluated earlier in the course of disease than when the disorder was first recognized.

The adrenal gland consists of two distinct regions, the outer cortex and inner medulla. The cortex consists of three distinct layers that produce mineralocorticoids (aldosterone), glucocorticoids and androgens.

Inflammatory liver disease is second only to hepatic lipidosis as a cause of hepatobiliary disease in cats in the United States. Inflammatory liver diseases have been traditionally classified by their cellular infiltrate and pattern of distribution.

Insulin has become increasingly important in the treatment of dogs and cats with diabetes mellitus. Almost all dogs are classified with insulin-dependent or type 1 diabetes mellitus.

The normal liver receives arterial blood from the hepatic artery and venous blood from the portal vein. Regarding arterial blood flow, the celiac artery branches off of the aorta and the hepatic artery branches off of the celiac artery.

The liver plays an important role in carbohydrate, lipid and protein metabolism as well as vitamin and mineral storage. The liver is also vital in detoxification of metabolic products (ammonia, uric acid), hormones and drugs.

The hypothalamus secretes thyrotropin-releasing hormone in response to nervous stimuli. The TRH then stimulates the pituitary gland to secrete thyrotropin-secreting hormone (TSH).

Naturally occurring hyperadrenocorticism (HAC) is an endocrine disorder resulting from the excess production of cortisol or other adrenal hormones by the adrenal cortex. The clinical syndrome was first documented in people by Dr. Harvey Cushing in 1932 and is also known as Cushing's syndrome.

A panel of veterinary specialists and general practitioners discuss their real-world experiences in providing successful care to diabetic cats.

This study establishes that there is a high prevalence of hyperadrenocorticism in dogs with gallbladder mucoceles and suggests that a similar association may be present between hypothyroidism and mucocele development.

Learn the latest on managing canine hyperadrenocorticism from Drs. Audrey K. Cook and David S. Bruyette (2 CE credits).

We asked you if you had questions for Dr. Audrey Cook about diabetes. Here are her responses.

A Q&A with veterinary endocrinologist Edward C. Feldman

There are 3 important fractions of calcium. This includes ionized calcium (45-50% of total calcium), which is the physiologically active fraction and is maintained within a fairly narrow range; protein-bound calcium (50-55% of total calcium) which is typically bound to albumin and is an inactive form of calcium; and complexed calcium, which in the normal patient accounts for less than 1-2% of total calcium, but can elevate the total calcium without affecting ionized calcium in chronic renal failure due to retention of substances such as citrate and oxalate that form calcium complexes.

Unfortunately, the cost of cosyntropin, the most reliable agent with which to perform an ACTH stimulation test, is expensive.

Acute thyrotoxicosis

Diabetes mellitus is a common endocrinopathy in canine practice, but successful patient management sometimes can be a challenge.

Pancreatitis: Inflammation of the pancreas

Feline Hyperthyroidism

Feline hyperthyroidism was first described in 1979 by Peterson and 1980 by Holzworth. It is now estimated that the incidence is as high as 2% of the feline population seen in tertiary veterinary care facilities.

Although only recently discovered, feline adrenal disorders are becoming increasingly more recognized. Feline adrenal disorders include diseases such as hyperadrenocorticism (Cushing's syndrome) and hyperaldosteronism (Conn's syndrome).