Lecture #19 - Low Circulating Calcium Response

Question 1

What does the parathyroid gland release in response to low circulating calcium, and what are the target organs?

Answer 1

1. The parathyroid gland releases parathyroid hormone (PTH)
2. which targets the liver to produce 25-OHD3
3. the kidneys to produce 1,25-OHD3 (Calcitriol)

4.and the bones to stimulate osteoclasts (break down bone and release calcium; calcium resorption).

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DRAWING IT OUT MIGHT HELP

Question 2

How does PTH affect the liver in calcium regulation?

Answer 2

PTH stimulates the liver to produce 25-OHD3, the first step in the activation of vitamin D.

Question 3

What role does PTH play in the kidneys?

Answer 3

PTH stimulates the kidneys to activate another hydroxylase that converts 25-OHD3 to 1,25-OHD3 (Calcitriol).

Question 4

How does calcitriol affect calcium reabsorption in the kidneys?

Answer 4

Calcitriol increases calcium reabsorption, reducing elimination and promoting retention of calcium.

Question 5

What is the effect of calcitriol on the intestines?

Answer 5

Calcitriol stimulates the expression of calcium transporters in the intestine, leading to increased calcium absorption.

Question 6

How does PTH influence bone resorption?

Answer 6

PTH activates osteoclasts in the bone to break down bone and release calcium into the bloodstream.