Hormonal Imbalances: Causes, Effects, and Key Endocrine Concepts
Endocrine Disorders and Hormonal Imbalances
Cushing’s Disease
Cushing’s disease is characterized by the excessive breakdown of tissue proteins and lipid reserves, and impaired glucose metabolism.
- Primary Cause: Overproduction of glucocorticosteroids.
Diabetes Insipidus: Key Symptoms
Polyuria
Polyuria is excessive urination associated with diabetes insipidus.
- Cause: Underproduction of ADH (Anti-Diuretic Hormone).
Polydipsia
Polydipsia is excessive thirst associated with diabetes insipidus.
- Cause: Associated with underproduction of ADH.
Growth-Related Hormonal Disorders
Acromegaly
Acromegaly is a hormonal disorder that results from too much growth hormone (GH).
Gigantism
Gigantism is a rare condition that causes abnormal growth in children. It occurs when a child’s pituitary gland produces too much growth hormone, which is also known as somatotropin.
Dwarfism
Dwarfism is a condition of short stature. The most common cause of dwarfism is a disorder called achondroplasia, which causes disproportionately short stature.
Adrenal Gland Conditions
Pheochromocytoma
A pheochromocytoma is a tumor in the adrenal gland. It causes the gland to make too much of the hormones epinephrine and norepinephrine.
Seasonal Affective Disorder (SAD)
A drop in serotonin, a brain chemical (neurotransmitter) that affects mood, might play a role in SAD. Reduced sunlight can cause a drop in serotonin that may trigger depression.
Key Hormones and Regulatory Systems
Bone Metabolism
Osteoclasts
Osteoclasts remove bone by dissolving the mineral and breaking down the matrix in a process that is called bone resorption. The osteoclasts come from the same precursor cells in the bone marrow that produce white blood cells. Excessive bone breakdown by osteoclasts is an important cause of bone fragility not only in osteoporosis but also in other bone diseases such as hyperparathyroidism.
Osteoblasts
Osteoblasts lay down bone in orderly layers that add strength to the matrix. Some of the osteoblasts are buried in the matrix as it is being produced and these are now called osteocytes.
Blood Pressure Regulation: Renin-Angiotensin System (RAS)
Angiotensin I
Angiotensin I is a decapeptide hormone that can be cleaved to the octapeptide angiotensin II.
Angiotensin II (AII)
Angiotensin II (AII) is an octapeptide, which is formed from angiotensin I within the RAS in a reaction catalyzed by angiotensin-converting enzyme (ACE), and it is a powerful vasoconstrictor.
Renin-Angiotensin System (RAS)
The Renin-Angiotensin System (RAS) plays a pivotal role in the development of atherosclerosis and hypertension, leading to congestive heart failure, myocardial infarction, and kidney damage.
Other Important Hormones
Aldosterone
Aldosterone, the main mineralocorticoid hormone, is a steroid hormone produced by the zona glomerulosa of the adrenal cortex.
Fundamental Endocrine Concepts
Hormones: Definition and Function
A hormone is a chemical substance produced in the body that controls and regulates the activity of certain cells or organs. It can also be defined as a molecule released by a cell or a gland in one part of the body that sends out messages affecting cells in other parts of the organism.
Endocrine System
The term endocrine relates to or denotes glands that secrete hormones or other products directly into the blood.
Homeostasis and Hormonal Control
To maintain homeostasis, the hypothalamus is responsible for creating or controlling many hormones in the body. The hypothalamus works with the pituitary gland, which makes and sends other important hormones around the body.
ADH and Water Balance
When the blood plasma becomes less concentrated and the level of ADH decreases, aquaporins are removed from collecting tubule cell membranes, and the passage of water out of urine and into the blood decreases.
Types of Endocrine Cells in the Pancreas
There are three main types of endocrine cells found in the pancreatic islets:
- Alpha cells: Secrete glucagon. Glucagon increases the blood glucose level by stimulating the liver to convert glycogen into glucose.
- Beta cells: Secrete insulin.
- Delta cells: Inhibit the secretion of glucagon and insulin.
Hormone Solubility Types
Water-Soluble Hormones
A water-soluble hormone is a lipophobic hormone that binds to a receptor on, or within, the plasma membrane, to initiate an intracellular signaling cascade.
Lipid-Soluble Hormones
A lipid-soluble hormone is a lipophilic hormone that passes through the plasma membrane of a cell, binds to an intracellular receptor, and changes gene expression.
Stress Response: General Adaptation Syndrome (GAS)
The General Adaptation Syndrome (GAS) describes the body’s response to stress and can be divided into three phases:
- The Alarm Phase: An immediate “fight or flight” response, under the direction of the sympathetic division of the Autonomic Nervous System (ANS).
- The Resistance Phase: Dominated by glucocorticoids.
- The Exhaustion Phase: The eventual breakdown of homeostatic regulation and failure of one or more organ systems.