Frederick H. Drazner, DVM, DACVIM

The endocrine pancreas is comprised of groups of cells (islets of Langerhans) scattered throughout the acinar parenchyma of the gland in a ratio of approximately 90% acinar cells (exocrine function) to 10% of islet cells (endocrine function). The pancreas is a boomerang-shaped organ comprised of two "wings" (duodenal and omental) in the cranial right quadrant of the abdomen.

In order for a hormone to be measured properly, with valid, repeatable results, the sample must be collected, stored and transported in a manner that is applicable for the hormone being tested. Obviously because various hormones have diverse chemical structures and physical properties, it is imperative that that the laboratory being utilized issue specific instructions and that these instructions be adhered to in order to achieve optimal results.

During the past 35 years there has been a dramatic emergence of both experimental and clinically applicable information in the subspecialty of endocrinology. With the development of such invaluable laboratory methodologies as radioimmunoassay (RIA), thinlayer chromatography (TLC), enzyme-linked immunosorbent assay (ELISA) and equilibrium dialysis (especially valuable in the measurement of free/unbound circulating hormones (ie., FT4).

Canine Hyperadrenocorticism (Canine Cushing's syndrome) is one of the more common endocrinopathies encountered in small animal practice; ranking behind only hypothyroidism and diabetes mellitus.

The pituitary gland is a small structure that adheres to the base of the diencephalons; just caudal to the optic chiasm. It is comprised of an anterior portion-the adenohypophysis(which is made up of the pars distalis and the pars intermedia) and a posterior portion termed the neurohypophysis (pars nervosa).

Management of the uncomplicated feline diabetic can occasionally be controlled by oral hypoglycemic agents (approximately 25-35%). This is because approximately 90% of the feline diabetic patients are similar to human Type2 diabetes mellitus (non-insulin dependent diabetes mellitus-NIDDM). However, by the time the cat is diagnosed with diabetes mellitus, the blood glucose is severely elevated (often>450 mg/dl) and many cats are ketotic, thus insulin is usually required.

The thyroid gland is made up of paired lobes on the ventrolateral surface of the proximal trachea. Felines may have accessory thyroid tissue in the neck and thorax. The size of the thyroid gland varies with the size of the dog; with medium-sized dogs having lobes approximately 5 cm. in length, 1.5 cm. in width, and 0.5 cm in thickness. In the average (4.5 kg) cat each lobe is approximately 2 cm.