Endocrine Physiology: Parathyroid Function

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Questions and Answers

What is the physiological importance of calcium in the body?

Storage of energy in cells

Nerve impulse transmission and muscle contraction (correct)

Formation of red blood cells

Regulation of blood pH

Which hormone acts indirectly to increase calcium absorption in the intestine?

Parathyroid hormone (correct)

Vitamin D3

Thyroid hormone

Calcitonin

Which of the following conditions is characterized by low levels of parathyroid hormone?

Thyroid storm

Hyperparathyroidism

Hypoparathyroidism (correct)

Adrenal insufficiency

What is one possible manifestation of hyperparathyroidism?

Elevated calcium levels in blood Signup and view all the answers

Tetany can be a clinical feature related to which condition?

Low calcium levels Signup and view all the answers

Parathyroid hormone primarily regulates calcium levels in the blood by acting on which organs?

Bones, kidneys, and intestines Signup and view all the answers

What can cause an inappropriate, excess secretion of parathyroid hormone?

Parathyroid adenomas Signup and view all the answers

Calcium homeostasis is primarily regulated by which of the following substances?

Parathyroid hormone and calcitonin Signup and view all the answers

What is the primary action of parathyroid hormone (PTH) in relation to calcium homeostasis?

Increase bone resorption Signup and view all the answers

Which hormone is primarily responsible for decreasing blood calcium levels?

Calcitonin Signup and view all the answers

What is the primary compensatory mechanism for hypocalcemia in secondary hyperparathyroidism?

Elevated levels of parathyroid hormone (PTH) Signup and view all the answers

What is one of the major functions of calcium in the body?

Involved in blood coagulation Signup and view all the answers

Which of the following manifestations is NOT associated with hyperparathyroidism?

Hypocalcemia Signup and view all the answers

Which of the following conditions may result from hypoparathyroidism?

Tetany due to low calcium levels Signup and view all the answers

What condition is characterized by the contractions of skeletal muscles due to decreased ionized plasma calcium levels?

Tetany Signup and view all the answers

Which of the following accurately describes the overall effect of Vitamin D3 on calcium homeostasis?

Promotes both calcium absorption and reabsorption Signup and view all the answers

Which test is NOT indicative of latent tetany?

Generalized convulsions Signup and view all the answers

What is the relationship between calcium levels and parathyroid hormone (PTH) secretion?

PTH secretion increases when calcium levels are low Signup and view all the answers

What happens to calcium levels in the blood as a result of hypoparathyroidism?

They decrease significantly. Signup and view all the answers

Which organ(s) are primarily influenced by calcitonin regarding calcium regulation?

Bone, kidneys, and intestine Signup and view all the answers

Which of the following statements about calcium homeostasis is accurate?

Vitamin D enhances intestinal absorption of calcium. Signup and view all the answers

What effect does hyperparathyroidism have on bone density?

Causes bone demineralization Signup and view all the answers

What is the effect of hyperparathyroidism on bone tissue?

Increased bone resorption Signup and view all the answers

What symptom is NOT typically associated with tetany?

Renal colics Signup and view all the answers

Study Notes

Endocrine Physiology: Parathyroid and Calcium Regulation

Parathyroid glands are small, bean-shaped glands located on the posterior surface of the thyroid gland. They exist in pairs.
Parathyroid hormone (PTH) is released from chief cells within the parathyroid glands.
PTH regulates calcium levels in the blood, a vital function.
Its main role is to increase plasma calcium levels and decrease plasma phosphate levels.
PTH works by acting on three target organs: bone, kidney, and intestine.
On bone, PTH increases bone resorption, releasing calcium from the bone matrix into the blood. Normal levels of PTH affect both osteoblasts and osteoclasts, but high levels only affect osteoclasts.
On the kidney, PTH increases calcium reabsorption and phosphate excretion.
On the intestine, PTH indirectly increases calcium absorption through its interaction with vitamin D3.
Calcium homeostasis is controlled by serum calcium levels.
There is no higher control of the parathyroid gland from the hypothalamus and pituitary.
Abnormalities in parathyroid hormone (PTH) secretion can lead to either hyperparathyroidism or hypoparathyroidism.
Hyperparathyroidism is characterized by excessive PTH secretion, resulting in increased blood calcium levels.
Causes of primary hyperparathyroidism include parathyroid gland abnormalities (adenomas).
Causes of secondary hyperparathyroidism include hypocalcemia (e.g., vitamin D3 deficiency or chronic renal failure).
Hypercalcemia (excess calcium in the blood) can lead to symptoms like stones (kidney stones), bones (bone pain and deformities), and abdominal groans (GI issues).
Hypoparathyroidism results in low PTH levels, leading to low blood calcium levels.
Causes include accidental removal of the parathyroid during thyroid surgery.
Hypocalcemia (low blood calcium) can manifest as tetany, a state of spastic muscle contractions due to increased neuromuscular excitability.
Manifest tetany usually appears during rest when calcium levels are below 7 mg%.
It has symptoms like carpopedal spasm, generalized convulsions, laryngeal and respiratory spasm, and suffocation.
Latent tetany may appear during stress when calcium levels are between 7-9mg%. It can be identified by tests like Trousseau's sign and Chvosteck's test.
Causes of tetany include decreased calcium intake, hypoparathyroidism, vitamin D3 deficiency, and renal failure.
Normal blood calcium levels are typically 9-11 mg/dL.
Vitamin D3 (1,25(OH)2D3) is crucial for maintaining calcium balance; it works on the intestine (increasing calcium absorption), kidneys (increasing calcium reabsorption), and bones (supporting osteoblast activity and bone matrix calcification).
Vitamin D3 production is initiated by sunlight on the skin.
Calcitonin is a hormone that decreases calcium levels in the blood. It is produced by parathyroid cells in the thyroid and counteracts the effects of PTH. The effects involve reducing bone resorption by inhibiting osteoclasts, increasing the excretion of calcium by the kidneys, and reducing absorption of calcium in the gut.

Calcium Homeostasis

Calcium (Ca) makes up 1.5% of total body mass, 99% stored in bones.

Plasma calcium levels are 9-11 mg/dL (average 10 mg/dL).

Calcium is in two forms, free/ionized (active) and bound (inactive).

Calcium metabolism involves intake from the diet, interchange and exchange with bones, and excretion.
There is a balance in the exchange between the intestine, blood, and kidneys in calcium metabolism to regulate normal levels in the body.

Functions of Calcium

Calcium is essential for:
- Bone and tooth formation
- Blood clotting
- Neuromuscular function and coupling
- Endocrine function and hormone actions

Hormones Involved in Calcium Homeostasis

Parathyroid Hormone (PTH): increases blood calcium levels
Vitamin D3: Increases blood calcium levels
Calcitonin decreased blood calcium levels

Vitamin D3 (1,25(OH)2D3) Function

Acts on the intestine: promotes calcium absorption from the digestive tract

Acts on the kidneys: increases calcium reabsorption

Acts on bones: promotes osteoblast activity and bone calcification

Calcitonin Function

Acts on bone to decrease bone resorption
Acts on kidneys to increase calcium excretion
Acts on the intestine to decrease calcium absorption.

Calcium Homeostasis Regulation

The body maintains a balance between PTH, vitamin D3, and calcitonin to monitor calcium in the blood, bones, and gut.
Blood calcium levels trigger the production or reduction of these hormones.

Assignment: Comparing Hormone Effects

Students need to compare the ways PTH, Calcitonin, and vitamin D3 impact calcium homeostasis.

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Description

This quiz explores the role of parathyroid glands and their hormone in regulating calcium levels in the body. It covers PTH's effects on bone, kidney, and intestine function, as well as its importance in maintaining calcium homeostasis. Test your knowledge on this crucial aspect of endocrine physiology.