Interaction of PTH & Vitamin D & Calcium

Question 1

What is the Interaction of PTH and Vitamin D and Calcium in the parathyroid gland?

Answer 1

● In parathyroid gland, 1,25 (OH) 2 D decreases PTH gene expression and consequently decreases amount of PTH available for secretion
● In the parathyroid gland, high serum levels of Ca2 + decrease synthesis and release of PTH by activating the membrane­bound calcium sensing receptor

Question 2

What is the Interaction of PTH and Vitamin D and Calcium in the kidney?

Answer 2

● In the kidney, PTH stimulates the production of 1,25(OH)2D and may reduce production of 24,25(OH)2D
● High serum Ca or PO4 levels lead to decreased production of the active 1,25 form of vitamin D in the kidney (and increase inactive 24,25 form)

Question 3

What is the indirect mechanism of regulating Calcium?

Answer 3

● Indirect mechanism of regulating Ca = calcium­phosphate complex
o This complex ties up Ca ions leading to a decrease in serum “free” Ca

Question 4

What does PTH do with calcium and phosphate?

Answer 4

Raise serum calcium concentration

Lower serum phosphate concentration

Question 5

What does Vitamin D do with calcium and phosphate?

Answer 5

Raise serum calcium concentration

Raise serum phosphate concentration