Adrenal Glands Overview
Posted: Tuesday, August 3rd, 2021 | Updated: Saturday, August 20th, 2022
Posted: Tuesday, August 3rd, 2021 | Updated: Saturday, August 20th, 2022
The Adrenal Glands
The adrenal glands are located adjacent to each kidney. They are composed of the outer adrenal cortex and the inner adrenal medulla. The adrenal cortex is formed by three layers. The outermost layer produces mineralocorticoid hormones. An example of a mineralocorticoid hormone would be aldosterone. Mineralocorticoids help the body regulate sodium and potassium levels by acting on the distal convoluted tubules in the kidneys. Sodium and water is absorbed while potassium is excreted. The middle layer produces glucocorticoid hormones which help metabolize nutrients and reduce inflammation by suppressing the immune response. An example of a glucocorticoid would be cortisol. The innermost layer produces the body’s sex hormones or androgens. The adrenal cortex is activated by adrenocorticotropic hormone (ACTH) produced by the pituitary gland. The adrenal medulla responds to stress, as well as low blood glucose levels. It releases catecholamines which increase heart rate, blood pressure, blood glucose, the body’s metabolic rate, and simultaneously slows digestion. Norepinephrine and epinephrine are examples of catecholamines
Hypoadrenocorticism (Addison’s Disease)
Addison’s disease is most notably documented in young to middle-aged dogs. It’s ultimately caused by a deficiency in adrenal gland hormones. Aldosterone is a mineralocorticoid hormone that typically helps to regulate various electrolytes. Note that whenever the body senses that kidney perfusion is decreased, aldosterone levels will typically increase in order to retain more sodium and water. When there’s little to no aldosterone being secreted or produced, potassium builds up in the bloodstream while sodium levels drop. Aldosterone helps retain sodium and water while excreting potassium. When aldosterone is not being produced, the increase in blood potassium levels can lead to arrhythmias and/or bradycardia. Eventually, these patients will go into shock. Symptoms of hypoadrenocorticism may include vomiting, diarrhea, inappetence, weight loss, and dehydration. Acute kidney failure is possible
Hyperadrenocorticism (Cushing’s Disease)
Cushing’s disease is a relatively common endocrine disease in adult dogs. Excess cortisol is produced resulting in polyuria, polydipsia, an increase in appetite, lethargy, heat intolerance, a pot-bellied appearance, thin skin, hair loss, bruising, and generalized weakness. Cortisol is a hormone that is active in carbohydrate metabolism, protein metabolism, blood pressure regulation, and blood glucose regulation. Cushing’s disease is usually caused by a benign pituitary gland tumor. Rarely, Cushing’s disease is caused by a tumor of the adrenal gland itself
The adrenal glands are located adjacent to each kidney. They are composed of the outer adrenal cortex and the inner adrenal medulla. The adrenal cortex is formed by three layers. The outermost layer produces mineralocorticoid hormones. An example of a mineralocorticoid hormone would be aldosterone. Mineralocorticoids help the body regulate sodium and potassium levels by acting on the distal convoluted tubules in the kidneys. Sodium and water is absorbed while potassium is excreted. The middle layer produces glucocorticoid hormones which help metabolize nutrients and reduce inflammation by suppressing the immune response. An example of a glucocorticoid would be cortisol. The innermost layer produces the body’s sex hormones or androgens. The adrenal cortex is activated by adrenocorticotropic hormone (ACTH) produced by the pituitary gland. The adrenal medulla responds to stress, as well as low blood glucose levels. It releases catecholamines which increase heart rate, blood pressure, blood glucose, the body’s metabolic rate, and simultaneously slows digestion. Norepinephrine and epinephrine are examples of catecholamines
Hypoadrenocorticism (Addison’s Disease)
Addison’s disease is most notably documented in young to middle-aged dogs. It’s ultimately caused by a deficiency in adrenal gland hormones. Aldosterone is a mineralocorticoid hormone that typically helps to regulate various electrolytes. Note that whenever the body senses that kidney perfusion is decreased, aldosterone levels will typically increase in order to retain more sodium and water. When there’s little to no aldosterone being secreted or produced, potassium builds up in the bloodstream while sodium levels drop. Aldosterone helps retain sodium and water while excreting potassium. When aldosterone is not being produced, the increase in blood potassium levels can lead to arrhythmias and/or bradycardia. Eventually, these patients will go into shock. Symptoms of hypoadrenocorticism may include vomiting, diarrhea, inappetence, weight loss, and dehydration. Acute kidney failure is possible
Hyperadrenocorticism (Cushing’s Disease)
Cushing’s disease is a relatively common endocrine disease in adult dogs. Excess cortisol is produced resulting in polyuria, polydipsia, an increase in appetite, lethargy, heat intolerance, a pot-bellied appearance, thin skin, hair loss, bruising, and generalized weakness. Cortisol is a hormone that is active in carbohydrate metabolism, protein metabolism, blood pressure regulation, and blood glucose regulation. Cushing’s disease is usually caused by a benign pituitary gland tumor. Rarely, Cushing’s disease is caused by a tumor of the adrenal gland itself
Sources:
Colville, Thomas, and Joanna M. Bassert. Clinical Anatomy and Physiology for Veterinary Technicians. 2nd ed. Mosby Elsevier, 2008.
Kahn, Cynthia M. The Merck/Merial Manual for Pet Health. Home Ed. Merck & Co., Inc. 2007.
Kingley, Jodi. "Fluid and Electrolyte Management in Parenteral Nutrition." Support Line. vol. 27, no. 6, December 2005, pp. 13.
Colville, Thomas, and Joanna M. Bassert. Clinical Anatomy and Physiology for Veterinary Technicians. 2nd ed. Mosby Elsevier, 2008.
Kahn, Cynthia M. The Merck/Merial Manual for Pet Health. Home Ed. Merck & Co., Inc. 2007.
Kingley, Jodi. "Fluid and Electrolyte Management in Parenteral Nutrition." Support Line. vol. 27, no. 6, December 2005, pp. 13.