Endocrine Regulation of Calcium II Flashcards Preview

Module 6: Repro/Endocrine > Endocrine Regulation of Calcium II > Flashcards

Flashcards in Endocrine Regulation of Calcium II Deck (18):
1

What hormone functions to lower plasma calcium? What cell produces it?

Calcitonin
Parafollicular (C-cells) of the thyroid

2

What hormones function to raise plasma calcium? What cell produces them?

PTH
Parathyroid chief cells

3

What is the distribution of calcium in the body?

99% in bone (hydroxyapatite)
1% in blood and soft tissues

4

What are the different forms of calcium in the blood?

45-50% ionized
5-10% Ca-salt complex
40-50% protein bound

5

What is the synthesis/activation pathway of Vitamin D2?

Ergosterol photooxidized by UV to Vit D2
Causes Beta ring to open

6

What is the synthesis/activation pathway of Vitamin D3?

7 dehydrocholesterol photooxidized by UV in the skin to vit D3
Causes Beta ring to open

7

What modification does the liver do to vitamin D?

25-hydroxylation

8

In what organ does 1alpha-hydroxylation and 24-hydroxylation of vitamin D?

Kidney

9

Under what circumstances is 24, 25-OH vitamin D formed?

Hypercalcemia

10

Under what circumstances is 1,25-OH vitamin D formed?

PTH, Estrogen and low serum Phosphate

11

What is the normal relationship between serum phosphorus and various forms of Vit-D?

High PO4 = 1,25-OH vit D
Low PO4 = 24,25-OH vit D

12

What are the causes post-menopausal and senile bone loss?

Low iPTH, estrogen, androgen, and 1alpha-hydroxylase result in inadequate 1,25 vitamin D.
This, in turn, reduces calcium absorption.

13

What form of Calcium is biologically active?

Free ionized Calcium

14

What are the effects of increased PTH?

Increases serum calcium and decreases phosphate
Increases bone reabsorption, Ca reabsorption from distal tubule and intestine, and P excretion from proximal tubule

15

What increases OPG secretion? What does OPG do?

Estrogen
OPG binds to RANKL preventing osteoblasts from stimulating osteoclast activity.

16

What results from a 1a-hydroxylase deficiency?

Vitamin D Dependent Rickets
Fixed by vitamin D supplementation

17

What causes Vitamin D Dependency rickets type II?

1,25-OHD target organ resistance

18

What are some treatments of osteoporosis?

Exercise
Estrogen (HRT)
Bisphosphonates
SERMS
Calcitonin
PTH
Denosumab