17.5 The Parathyroid Glands
2 min read•june 18, 2024
The , tiny organs behind the thyroid, play a crucial role in calcium regulation. They produce ###parathyroid_hormone_()_0###, which works to increase blood calcium levels by targeting bones, kidneys, and intestines.
Disorders of the can lead to serious health issues. causes high calcium levels and weakened bones, while results in low calcium, muscle cramps, and potentially dangerous complications like seizures.
Parathyroid Glands
Location and structure of parathyroid glands
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- Embedded in the posterior surface of typically four glands: two superior and two inferior
- Small, oval-shaped glands composed of and
- secrete (PTH) which regulates calcium levels in the body
- Oxyphil cells have an unknown function but are present in higher numbers in older individuals
Parathyroid hormone and calcium regulation
- Parathyroid hormone (PTH), also known as , functions to increase blood calcium levels when they fall below normal by targeting bones, kidneys, and intestines to maintain
- Effects on bones:
- Stimulates to break down bone matrix and release calcium into the bloodstream ()
- Increases calcium reabsorption from bone fluid
- Effects on kidneys:
- Enhances reabsorption of calcium in the distal tubules and collecting ducts
- Reduces reabsorption of phosphate, leading to increased phosphate excretion
- Stimulates the production of active () which increases intestinal absorption of calcium
- Effects on intestines: PTH indirectly increases calcium absorption through its effect on calcitriol production in the kidneys
Effects of parathyroid disorders
- involves excessive secretion of PTH due to enlargement or tumors of the parathyroid glands (primary) or as a compensatory response to chronic low blood calcium levels (secondary)
- Effects include (elevated blood calcium), weakened bones due to increased bone resorption, formation of kidney stones due to increased calcium excretion, and symptoms like fatigue, muscle weakness, and depression
- Prolonged hyperparathyroidism can lead to , a condition characterized by decreased bone density and increased risk of fractures
- involves insufficient secretion of PTH often due to damage or removal of parathyroid glands during thyroid surgery, autoimmune disorders, or genetic factors
- Effects include (low blood calcium), muscle cramps, twitches, and spasms, tingling sensations in the fingers and toes, and in severe cases seizures and cardiac arrhythmias
- In extreme cases, hypoparathyroidism can lead to , a condition characterized by severe muscle spasms and convulsions
Calcium Homeostasis and the Endocrine System
- The parathyroid glands are part of the , which regulates various bodily functions through hormone secretion
- , a hormone produced by the , works in opposition to PTH by lowering blood calcium levels
- The interplay between PTH and helps maintain calcium homeostasis in the body
Key Terms to Review (37)
Bone Resorption: Bone resorption is the process by which osteoclasts break down and remove old or damaged bone tissue, releasing the minerals and other components back into the body. This process is essential for the continuous remodeling and maintenance of healthy bone structure throughout an individual's lifetime.
Calcitonin: Calcitonin is a hormone produced by the thyroid gland that helps regulate calcium levels in the blood by lowering them when they are high. It acts by inhibiting the activity of osteoclasts, cells that break down bone, thereby reducing the release of calcium from bones.
Calcitonin: Calcitonin is a hormone produced by the thyroid gland that plays a crucial role in regulating calcium homeostasis within the body. It functions to lower blood calcium levels by inhibiting the activity of osteoclasts, the cells responsible for bone resorption, and promoting the deposition of calcium into bone tissue.
Calcitriol: Calcitriol, also known as 1,25-dihydroxyvitamin D3, is the active form of vitamin D that plays a crucial role in calcium homeostasis, the regulation of parathyroid gland function, and the maintenance of urinary system homeostasis. It is a steroid hormone that is produced in the kidneys and has widespread effects throughout the body.
Calcium Homeostasis: Calcium homeostasis is the process by which the body maintains a stable concentration of calcium in the blood and extracellular fluids. This delicate balance is crucial for various physiological functions, including bone health, muscle contraction, nerve impulse transmission, and blood clotting.
Calcium Homeostasis: Interactions of the Skeletal System and Other Organ Systems: Calcium homeostasis is the regulation of calcium levels in the bloodstream, primarily controlled by the skeletal system, kidneys, and parathyroid glands to maintain optimal physiological conditions. It involves the processes of calcium absorption, storage, and mobilization to ensure stable calcium concentrations for various bodily functions.
Calcium-Sensing Receptor: The calcium-sensing receptor (CaSR) is a G-protein coupled receptor that acts as a molecular sensor, detecting changes in extracellular calcium concentrations and initiating signaling cascades to maintain calcium homeostasis within the body. This receptor plays a crucial role in the regulation of calcium levels, particularly in the interactions between the skeletal system and other organ systems, as well as in the function of the parathyroid glands.
Chief cells: Chief cells are specialized cells located in the lining of the stomach that secrete pepsinogen, an inactive enzyme that is converted into pepsin to break down proteins during digestion. They play a crucial role in the digestive process by initiating protein digestion.
Chief Cells: Chief cells, also known as principal cells, are the predominant secretory cells found in the gastric glands of the stomach. These cells are responsible for producing and secreting pepsinogen, the inactive precursor of the digestive enzyme pepsin, which is essential for the breakdown of proteins in the stomach.
Development and Aging of the Endocrine System: The process by which the endocrine system evolves and changes in structure and function from birth through old age, impacting hormone production and regulation. It encompasses both the maturation of this system during childhood and adolescence, as well as its gradual decline in efficiency as part of the natural aging process.
Dihydroxyvitamin D: Dihydroxyvitamin D is a form of vitamin D that is crucial for the regulation of calcium and phosphate levels in the bloodstream, promoting healthy bone formation and maintenance. It is produced in the body through a process involving skin exposure to sunlight, liver transformation, and finally activation in the kidneys.
Endocrine System: The endocrine system is a complex network of glands and organs that produce and secrete hormones, chemical messengers that regulate various physiological processes in the body. It works in coordination with the nervous system to maintain homeostasis and ensure the proper functioning of the body's systems, including metabolism, growth, development, and reproduction.
Hypercalcemia: Hypercalcemia is a condition characterized by abnormally high levels of calcium in the blood. It can result from overactive parathyroid glands, certain cancers, or excessive intake of vitamin D or calcium.
Hypercalcemia: Hypercalcemia is a condition characterized by an abnormally high level of calcium in the blood. This imbalance can have significant impacts on the skeletal system, parathyroid glands, and electrolyte balance within the body.
Hyperparathyroidism: Hyperparathyroidism is a condition characterized by the excessive production of parathyroid hormone (PTH) by the parathyroid glands, which are four tiny glands located near or attached to the back side of the thyroid gland. This overproduction leads to high levels of calcium in the blood, affecting various body systems.
Hyperparathyroidism: Hyperparathyroidism is a condition characterized by excessive production of parathyroid hormone (PTH) by the parathyroid glands. This leads to an imbalance in the regulation of calcium and phosphate levels in the body, with far-reaching effects on various physiological processes.
Hypocalcemia: Hypocalcemia is a condition characterized by an abnormally low level of calcium in the blood. It can disrupt various bodily functions, particularly within the bone tissue and the skeletal system, affecting bone density and strength.
Hypocalcemia: Hypocalcemia is a condition characterized by an abnormally low level of calcium in the blood. This electrolyte imbalance can have significant impacts on the skeletal system, parathyroid gland function, and overall electrolyte balance in the body.
Hypoparathyroidism: Hypoparathyroidism is a condition where the parathyroid glands produce insufficient amounts of parathyroid hormone (PTH), leading to decreased calcium levels in the blood. This hormonal imbalance can affect various bodily functions, including bone health, nerve transmission, and muscle contraction.
Hypoparathyroidism: Hypoparathyroidism is a medical condition characterized by an underactive parathyroid gland, resulting in an abnormally low level of parathyroid hormone (PTH) in the body. This hormonal imbalance leads to a disruption in the regulation of calcium and phosphorus levels, which are essential for various physiological processes.
Negative Feedback Loop: A negative feedback loop is a self-regulating mechanism in biological systems where the output of a process inhibits or reduces the initial stimulus, maintaining homeostasis and stability within the system. It is a key regulatory mechanism that helps the body maintain optimal physiological conditions.
Osteoclasts: Osteoclasts are large, multinucleated cells responsible for the resorption and breakdown of bone tissue. They play a crucial role in the remodeling and maintenance of the skeletal system, as well as in the regulation of calcium homeostasis within the body.
Osteoporosis: Osteoporosis is a condition characterized by weakened bones, making them more susceptible to fractures. It occurs when the creation of new bone doesn't keep up with the removal of old bone.
Osteoporosis: Osteoporosis is a progressive, systemic skeletal disease characterized by low bone mass and microarchitectural deterioration of bone tissue, leading to enhanced bone fragility and a consequent increase in fracture risk. This condition is closely related to the topics of tissue injury and aging, bone formation and development, exercise and nutrition's impact on bone, parathyroid gland function, endocrine system changes with aging, and the importance of proper nutrition for bone health.
Oxyphil cells: Oxyphil cells are specialized cells found in the parathyroid glands, characterized by their large size and eosinophilic staining properties due to their abundant mitochondria. These cells are thought to play a role in the regulation of calcium levels in the body, although their precise function remains less understood compared to the more prominent chief cells that secrete parathyroid hormone (PTH). Oxyphil cells may also increase in number with age, indicating a potential link to changes in parathyroid function over time.
Parathormone: Parathormone, also known as parathyroid hormone (PTH), is a peptide hormone produced by the parathyroid glands that plays a critical role in regulating calcium levels in the blood and bone metabolism. This hormone is essential for maintaining the balance of calcium and phosphorus in the body, influencing processes like bone resorption, renal calcium reabsorption, and intestinal calcium absorption.
Parathyroid glands: The parathyroid glands are small, pea-sized glands located on the posterior surface of the thyroid gland in the neck. They produce parathyroid hormone (PTH), which regulates calcium levels in the blood and bone metabolism.
Parathyroid Glands: The parathyroid glands are a group of small endocrine glands located in the neck, typically near or attached to the posterior surface of the thyroid gland. They are responsible for the regulation of calcium and phosphate levels in the body through the production and secretion of parathyroid hormone (PTH).
Parathyroid Hormone: Parathyroid hormone (PTH) is a polypeptide hormone produced by the parathyroid glands that plays a crucial role in maintaining calcium homeostasis within the body. It is a key regulator of bone formation and development, as well as the interactions between the skeletal system and other organ systems, particularly the endocrine system.
Parathyroid hormone (PTH): Parathyroid hormone (PTH) is a peptide hormone produced and released by the parathyroid glands, playing a crucial role in regulating calcium levels in the blood. It increases calcium levels by stimulating bone resorption, increasing intestinal calcium absorption, and promoting kidney reabsorption of calcium.
Phosphate Regulation: Phosphate regulation refers to the body's intricate system of maintaining proper levels of phosphate, a critical mineral involved in various physiological processes. This term is particularly relevant in the context of the parathyroid glands, which play a central role in regulating phosphate homeostasis.
Posterior Thyroid: The posterior thyroid, also known as the parathyroid gland, is a small endocrine gland located on the posterior surface of the thyroid gland. It is responsible for the production and secretion of parathyroid hormone, which plays a crucial role in regulating calcium and phosphate homeostasis within the body.
PTH: PTH, or parathyroid hormone, is a crucial hormone produced by the parathyroid glands that plays a central role in regulating calcium and phosphate homeostasis within the body. It is intimately connected to the topics of 'An Overview of the Endocrine System' and 'The Parathyroid Glands'.
Tetany: Tetany is a neuromuscular disorder characterized by involuntary muscle contractions and spasms, often caused by a deficiency or imbalance of certain electrolytes, particularly calcium. This condition is closely linked to the regulation of calcium homeostasis, the function of the parathyroid glands, and acid-base balance in the body.
The Thyroid Gland: The thyroid gland is a butterfly-shaped endocrine gland located in the front lower part of the neck, responsible for producing hormones that regulate the body's metabolic rate as well as heart and digestive function, muscle control, brain development, and bone maintenance. Its proper functioning is essential for overall health and well-being.
Thyroid Gland: The thyroid gland is an endocrine gland located in the front of the neck that plays a crucial role in regulating the body's metabolism, growth, and development. It produces hormones that are essential for maintaining homeostasis and proper functioning of various systems throughout the body.
Vitamin D: Vitamin D is a fat-soluble vitamin that plays a crucial role in maintaining bone health, calcium homeostasis, and various other physiological processes in the body. It is often referred to as the 'sunshine vitamin' because the human body can synthesize it when the skin is exposed to ultraviolet B (UVB) radiation from sunlight.
Vitamin D is closely linked to the topics of bone formation and development, exercise, nutrition, and calcium homeostasis. It also has important interactions with the parathyroid glands, organs with secondary endocrine functions, chemical digestion and absorption, and overall nutrition and diet.