Session 11- Parathyroid Gland and Calcium and Phosphate metabolism

Question 1

What hormone elevates serum calcium

Answer 1

Parathyroid hormone

Question 2

What is calcitrol also known as

Answer 2

1,25 (OH) 2D

Question 3

How is PTH synthesis regulated

Answer 3

Low serum calcium up regulates gene transcription

High serum calcium down-regulate

Low serum calcium prolongs survival of mRNA

Question 4

What do chief cells do when PTH levels get too high

Answer 4

They degrade PTH and it is accelerated by high serum calcium levels

Question 5

What kind of receptor does calcium bind to

Answer 5

G protein couple receptor

G alpha q

Question 6

Affect on PTH on bone

Answer 6

Increase resorption- oseoclast activity

Question 7

Affect of PTH on intestine

Answer 7

Activates calcitriol/vit D and hence increases transcellular uptake from GI tract

PTH stimulates conversion of vitamin D to its active form which
↑uptake of Ca2+ from gut.

Question 8

Affect of PTH on kidney

Answer 8

Decreases loss to urine

Question 9

What are the primary functions of the skeleton- calcium

Answer 9

Structural support and maintaining serum Ca2+ concentration

Maintenance of serum Ca2+ conc is priority

Question 10

How does bone deposition occur

Answer 10

Osteoblasts produce collagen matrix which is mineralised by hydroxyapatite

Question 11

How does bone reabsorption

Answer 11

Osteoclasts produce acid micro-environment hydroxyapatite dissolves

Question 12

What three physiochemical forms does Calcium exis in

Answer 12

• free ionised species
• bound to anionic sites on serum proteins- albumin
• complexed with low-molecular-weight organic anions

Question 13

Which form of calcium is physiologically active

Answer 13

Free ionised calcium

Question 14

What role does calcium play

Answer 14

Hormone processes 
Muscle contraction 
Nerve conduction 
Exocytosis 
Activation of many enzymes

Question 15

Why are calcium and phosphate so important

Answer 15

There are h principal component for hydroxyapatite crystals which constitute by far the major portio of the mineral phase of bone

They are regulated by the same hormones primarily PTH and calcitrol and to a lesser extent calcitonin

Question 16

Effects of hypocalcaemia

Answer 16

Hyper-excitability in the neuromuscular junction leading to paraesthesia the tetany, paralysis and even conclusions

-lower serum calcium causes increase in Na+ entry into neurones, leading yo a depolarisation and increase likelihood of AP

Question 17

Effects of hypercalcaemia

Answer 17

Formation of kidney sones, constipation, dehydration, kidney damage, tiredness and depression

Question 18

Which hormones raise serum calcium

Answer 18

PTH

Calcitrol

Question 19

What is calcitrol

Answer 19

An active form of vitamin D

Question 20

What is responsible for long term regulation of calcium

Answer 20

Calcitrol

Question 21

What is responsible for short term regulation of calcium

Answer 21

PTH

Question 22

How is Vit D obtained

Answer 22

Sun exposure, food and supplements

Question 23

How is vit D activated

Answer 23

Hydroxylation

Question 24

What type fo hormone is PTH

Answer 24

Peptide

Question 25

What is calcitonin

Answer 25

peptide hormone produced by the parafollicular cells of the thyroid gland, secreted in response to high levels of plasma Ca2+ and also in response to GI hormones- gastrin decreases plasma Ca2+ decreases plasma phosphate levels

Question 26

Cellular roles of calcium

Answer 26

``` • Neuromuscular excitability • Coagulation • Synaptic transmission • Second messenger for hormones and growth factors • Regulation of gene transcription • Coordination of Metabolic activity • Bone formation ```

Question 27

cellular roles of phosphate

Answer 27

* Structure of membrane phospholipids * Energy metabolism (e.g. ATP) * Protein phosphorylation * Genetic information (DNA/RNA) * Bone formation

Question 28

How does plasma calcium control differ from Na+ and K+ control in 2 important ways

Answer 28

1) The extent Ca2+ absorption from the G.I. tract is hormonally controlled and depends on Ca2+ status of the body (K+ and Na+ homeostasis is maintained primarily by regulating urinary excretion……controlled output matches uncontrolled input) 2) Bone serves as a large Ca2+ reservoir that can be drawn on to maintain free plasma Ca2+ levels (Similar in-house stores not available for K+ and Na+)

Question 29

how do you measure serum calcium

Answer 29

• Venous blood sample drawn into plain tube (no anticoagulant) • Albumin measured at the same time

Question 30

what do high serum alkaline phosphatase indicate

Answer 30

• High plasma levels correlate with increased bone formation marker of increased bone turnover

Question 31

What 2 ways can malignancy cause hypercalaemia

Answer 31

Haematological malignancies- those that metastisize to bone and produce local factors that act in a paracrine manner to activate osteoclasts squamous tumours of the lung, head and neck produce a hormone, PTHrp that acts at parathyroid hormone receptors

Question 32

normal physiological roles of PTHrp

Answer 32

tooth eruption mammary gland development lactation placental transfer of calcium

Question 33

what cells produce PTH

Answer 33

chief cells of the parathyroid gland

Question 34

role of PTH

Answer 34

regulate levels of Ca2+ AND PHOSPHATE IN BLOOD increases plasma calcium levels decreases plasma phosphate level

Question 35

fast exchange of calcium between bone and blood

Answer 35

In a fast exchange, Ca2+ is moved from the labile pool in the bone fluid into the plasma by means of PTH-activated Ca2+ pumps located in the osteocytic-osteoblastic bone membrane

Question 36

slow exchange of Ca2+ between bone and blood

Answer 36

Ca2+ is moved from the stable pool in the mineralised bone into the plasma by means of PTH-induced dissolution of the bone