Endocrine System
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Endocrine System IntroductionThe endocrine system encompasses a group of tissues that release hormones into circulation. Hormones are signaling molecules that travel to targets distant from their site of production and interact with receptors to exert their effects. Some act only on a single tissue; others have effects on nearly all cells of the body. The effects of hormones on their targets vary—from enhancement of nutrient uptake to alteration of cell division and differentiation, among many others.
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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
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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.
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The Parathyroid Glands and Disorders of Calcium Regulation in Dogs and CatsCalcium plays an essential role in normal biochemical and physiologic mechanisms in the body and has a complex homeostatic system. The parathyroid glands are integral to this homeostasis, and disorders of the parathyroid glands result in abnormal calcium homeostasis. Testing for diseases affecting calcium homeostasis will usually focus on evaluating concentrations of total calcium, ionized calcium, parathyroid hormone (PTH), phosphorus, parathyroid hormone-related protein (PTHrP), and vitamin D metabolites.
- Overview of the Parathyroid Glands and Disorders of Calcium Regulation in Dogs and Cats
- Physiology and Calcium-Regulating Hormones in Dogs and Cats
- Hypercalcemia in Dogs and Cats
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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
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Neuroendocrine TumorsNeuroendocrine tumors are a diverse family of neoplasms affecting many organs and tissues. Some are functional (ie, release a hormone product). Clinical signs vary, from syndromes of hormone excess to effects related to size and expansion of the tumor (mass effect). Neuroendocrine tumors may be found incidentally in the course of imaging studies or at necropsy. Treatment options vary, from surgical removal to medical treatment.
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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.
