Parathyroid physiology

Question 1

What stimulates the parathyroid gland to release PTH?

Answer 1

Decreased calcium

Question 2

Where is vitamin D3 produced?

Answer 2

Skin

Question 3

How is calcidiol produced?

Answer 3

Converted from Vit D3 in the liver

Question 4

What enzyme converts calcidiol to calcitriol?

Answer 4

a-hydroxylase

Question 5

What does PTH stimulate?

Answer 5

Kidney (a-hydroxylase to convert calcidiol to calcitriol)
Bone (release calcium & phosphate)
DCT (increase calcium reabsorption)

Question 6

What exhibits a negative feedback mechanism on PTH?

Answer 6

Calcitriol

Question 7

Whatdoes calcitriol stimulate?

Answer 7

Bone (release calcium & phosphate)
GI tract (absorb calcium & phosphate)
PCT (reabsorb calcium)

Question 8

What stimulates release of calcitonin from the thyroid gland?

Answer 8

Decreased calium

Question 9

What is the parathyroid gland composed of?

Answer 9

Chief cells

Question 10

Symptoms/signs of hyperparathyroidism

Answer 10

Bone disease (pain, fracture, osteoporosis)
Renal stones
GI (constipation, nausea, peptic ulcer, gallstones, pancreatitis)
CNS (depression, lethargy, seizures)
Muscular weakness & fatgue
CVS (Calcification of aortic + mitral valves)

Question 11

Causes of hperparathyroidism

Answer 11

Adenoma

Hyperplasia

Question 12

Management of hyperparathyroidism

Answer 12

Surgery

Question 13

Indications for parathyroid surgery

Answer 13

End organ damage

Very high calcium (>2.85)

Question 14

What is primary hyperparathyroidism?

Answer 14

Primary overactivity of parathyroid (e.g.adenoma)

Question 15

What are the biochemical findings of primary hyperparathyroidism?

Answer 15

High PTH
High Calcium
Normal Alk Phos
Low phosphate

Question 16

What is secondary hyperparathyroidism?

Answer 16

Physiological response to low calcium due to chronic hypocalcaemia
(parathyroid is hyperplastic)

Question 17

Causes of secondary hyperparathyroidism

Answer 17

Renal failure
Low calcium intake
Vit D deficiency

Question 18

Biochemical findings of secondary hyperparathyroidism

Answer 18

Low calcium

High PTH

Question 19

What is tertiary hyperparathyroidism?

Answer 19

Parathyroid becomes autonomous after many years of secondary

Question 20

Biochemical findings of tertiary hyperparathyroidism

Answer 20

High calcium

High PTH

Question 21

What can be a congenital cause of absent parathyroid glands?

Answer 21

Di George syndrome

Question 22

Causes of hypoparathyroidism

Answer 22

Congenital abscence
Destruction (surgery, malignancy, radiotherapy)
Autoimmune
Hypomagnaesmia

Question 23

Treatment of hypoparathyroidism

Answer 23

Calcium & Vitamin D supplements

Question 24

What is a mild type of osteogenesis imperfecta?

Answer 24

Type I

Question 25

What are the severe types of osteogenesis imperfecta?

Answer 25

Types III & IV

Question 26

Which type of osteogenesis imperfecta causes nneonatsl death?

Answer 26

Type II

Question 27

What is osteogenesis imperfecta associated with?

Answer 27

Blue sclerae | Dentinogenesis

Question 28

Management of osteogenesis imperfecta

Answer 28

No cure | Bisphosphonates

Question 29

Causes of vitamin D deficiency

Answer 29

Dietary deficiency Malabsorption Chronic renal failure Drugs (anti-convulsants)

Question 30

Features of osteomalacia

Answer 30

Low calcium Proximla muscle wasting Dental defects Bone tenderness

Question 31

What mutation causes vitamin D resistant rickets?

Answer 31

PHEX gene mutation

Question 32

Treatment of vitamin D resistant rickets

Answer 32

Phosphate + Vit D3

Question 33

Why does hypomagnasaemia affect calcium levels?

Answer 33

Calcium release from cells is dependent on magnesium Means increased intracellular calcium PTH release is inhibited Skeletal + muscles receptors less sensitive to PTH

Question 34

Cuases of hypomagnasaemia

Answer 34

Alcohol (+/- PPI) Drugs (thiazide, PPI) GI illness (malabsorption) Pancreatitis

Question 35

What is pseudohyperparathyroidism a genetic defect of?

Answer 35

GNAS 1

Question 36

Biochemical findings of pseudohyperparathyroidism

Answer 36

Low calcium | High PTH

Question 37

Features of pseudohyperparathyroidism

Answer 37

``` Bone abnormalities (McCune Labright) Obesity Subcutaneous calcification Learning diability Brachdactyly (4th metacarpal) ```

Question 38

Difference between pseudohyperparathyroidism & pseudo-pseudohyperparathyroidism

Answer 38

Pseudo-pseudo has normal calcium | patients can change from pseudo to pseudo-pseudo

Question 39

What is Paget's disease?

Answer 39

Abnormal osteoclastic activity followed by increased osteoblastic activity = abnormal bone structure

Question 40

Which bones are typically affected by Paget's?

Answer 40

Long bones Pelvis Lumbar spine Skull

Question 41

How does Paget's present?

Answer 41

Incidenc increases with age Bone pain Deformity Deafness

Question 42

What is a rare complication of Paget's?

Answer 42

Osteosarcoma

Question 43

Treatment of Paget's

Answer 43

Treat with bisphosphates if pain not responding to analgesia

Question 44

Biochemical findings of FHH

Answer 44

High calcium Normal PTH Normal Alk Phos Normal phosphate

Question 45

Biochemical findings of hypoparathyroidism

Answer 45

Low calcium Low PTH Normal Alk Phos Normal phosphate

Question 46

Biochemical findings of osteomalacia

Answer 46

Low calcium High PTH High Alk Phos Low phosphate

Question 47

Biochemical findings of Paget's

Answer 47

Normal calcium Normal PTH High Alk Phos Normal phosphate