Hormonal Regulation of Calcium

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Questions and Answers

What effect does an increase in ionized Ca2+ have on PTH secretion?

Has no effect on PTH secretion
Increases PTH production rate
Stimulates PTH secretion
Inhibits PTH secretion (correct)

Which hormone is primarily responsible for bone resorption?

Insulin
PTH (correct)
Vitamin D
Calcitonin

How does PTH affect calcium in the kidneys?

Increases calcium reabsorption (correct)
Decreases calcium reabsorption
Has no effect on calcium levels
Stimulates calcium excretion

What stimulates the secretion of PTH in the blood?

<p>Decreased ionized Ca2+ levels (B)</p> Signup and view all the answers

What role does PTH have in relation to vitamin D?

<p>Stimulates renal production of active vitamin D (D)</p> Signup and view all the answers

Flashcards

Parathyroid Hormone (PTH)

A hormone that plays a vital role in regulating calcium levels in the blood. It's released when calcium levels are low and helps increase calcium levels by promoting bone breakdown, enhancing calcium reabsorption in the kidneys, and stimulating vitamin D production.

How does PTH affect bone?

A hormone that activates osteoclasts, specialized cells that break down bone, releasing calcium into the bloodstream.

How does PTH affect the kidneys?

PTH increases the reabsorption of calcium ions in the kidneys, preventing them from being excreted in urine.

Vitamin D

A fat-soluble vitamin that regulates calcium absorption in the gut. It's produced in the body and its production is stimulated by PTH.

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Calcitonin

A hormone that promotes calcium storage in bones and decreases calcium levels in the blood. It's released when calcium levels are high.

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Study Notes

Calcium Regulation by Hormones

Three hormones—PTH, vitamin D, and calcitonin—control serum calcium (Ca2+) levels.
They adjust secretion in response to ionized calcium (Ca2+) changes.
Parathyroid hormone (PTH) secretion increases when ionized Ca2+ levels decrease and decreases when ionized Ca2+ levels rise.
PTH has key effects on bone and kidneys.
In bone, PTH activates bone resorption, where osteoclasts break down bone, releasing calcium into the extracellular fluid (ECF).
In kidneys, PTH promotes calcium reabsorption in tubules.
PTH also stimulates the kidneys to produce active vitamin D.