Endocrine System
-
Endocrine System IntroductionThe endocrine system encompasses a group of tissues that release hormones into circulation for travel to and action on distant targets. An endocrine tissue is typically a ductless gland (eg, pituitary, thyroid) that releases its hormones into capillaries that permeate the tissue. These glands are richly supplied with blood. However, nontypical endocrine tissues also contribute important hormones to circulation, eg, secretion of atrial natriuretic peptide from the heart, erythropoietin from the kidney, insulin-like growth factor from the liver, and leptin from fat. New hormones continue to be discovered. Some act only on a single tissue, whereas others have effects on virtually all cells of the body. The effects of hormones on their targets are varied—from enhancement of nutrient uptake to altering cell division and differentiation, among many others.
-
The Pituitary GlandThe pituitary gland (hypophysis) is composed of the adenohypophysis (anterior lobe) and the neurohypophysis (posterior lobe).
- The Pituitary Gland in Animals
- Cushing Disease (Pituitary-dependent Hyperadrenocorticism) in Animals
- Nonfunctional Pituitary Tumors in Animals
- Hypertrichosis Associated with Adenomas of the Pars Intermedia
- Adult-onset Panhypopituitarism in Animals
- Juvenile-onset Panhypopituitarism in Dogs
- Diabetes Insipidus in Animals
- Feline Acromegaly
-
The Thyroid GlandAll vertebrates have a thyroid gland. In mammals, it is usually bilobed and located just caudal to the larynx, adjacent to the lateral surface of the trachea. The two lobes may be connected by a fibrous isthmus (eg, ruminants, horses), or a connecting isthmus may be indistinct (eg, dogs, cats). The gland is extremely vascular. In birds, it is found within the thoracic cavity; both lobes are located near the syrinx, adjacent to the carotid artery near the origin of the vertebral artery.
-
The Parathyroid Glands and Disorders of Calcium MetabolismThe physiology and disorders of calcium and phosphate metabolism, the function of vitamin D (which acts more like a hormone than a vitamin), and the formation of bone are all tied together in a common system along with two other regulatory hormones—parathyroid hormone (PTH) and calcitonin. Therefore, PTH, calcitonin, and vitamin D are discussed in this chapter together with the associated disorders of calcium homeostasis.
- Overview of the Parathyroid Glands and Disorders of Calcium Metabolism
- Calcium Physiology and Calcium-regulating Hormones
- Hypercalcemia in Dogs and Cats
- Hypercalcemia in Horses
- Hypocalcemia in Dogs and Cats
- Hypocalcemic Disorders of Horses
-
The Adrenal GlandsThe adrenal glands are essential for life, being responsible for the minute-to-minute regulation of blood pressure, blood volume, and vascular tone. Originally, their actions were thought to be limited to the "flight or fight phenomenon, but with increased knowledge of the many actions of aldosterone and aldosterone excess there has been renewed interest in the adrenal glands with respect to health and disease.
- Overview of the Adrenal Glands
- Adrenal Cortex
- Cushing Syndrome (Hyperadrenocorticism)
- Addison Disease
- Feline Primary Hyperaldosteronism
- Adrenal Medulla
-
Neuroendocrine TumorsNeuroendocrine tumors (NETs) are a diverse family of neoplasms affecting many organs and tissues. Some are functional, ie, they release their normal hormone product, and many are non-functional. Clinical signs vary, from syndromes of hormone excess to effects related to size and expansion of the tumor (mass effect). Other NETs are found incidentally in the course of imaging studies. Some are only identified at necropsy.
-
The PancreasThe endocrine function of the pancreas, production of insulin and other hormones, is performed by small groups of cells, the islets of Langerhans. The islets are completely surrounded by acinar (exocrine) cells that produce digestive enzymes. The endocrine and exocrine portions of the pancreas are closely related during development, and evidence suggests that islet, acinar, and ductal cells arise from a common multipotential precursor cell.
