Parathyroid

Question 1

What is parathyroid hormone (PTH)?

What does it do?

Answer 1

Hormone synthesised and released by the parathyroid gland in response to hypocalaemia.

It increases calcium levels by

• increasing osteoclastic activity which resorbs bone
• increases renal reabsoroption of calcium
• acts on kidneys to convert 20(OH) vitamin D to active calcitriol (1,25 OH vitamin d) which acts on the gut to increase calcium absorption

Question 2

What is calcitonin?

What does it do?

Answer 2

Hormone released by parafollicular cells of the thyroid gland.

Decreases calcium levels by

• decreasing osteoclastic activity
• inhibiting renal reabsorption of calcium

Question 3

How is calcium absorbed in the gut?

Answer 3

Generally, poorly.

Calcitriol acts on the gut to increase calcium absorption

Question 4

Outline the steps involved in vitamin D synthesis and activation.

Answer 4

1. Vitamin D enters body from
   - Sunlight (converts dehydroxyxholseterol to vitamin D in keratinocytes)
   - Diet (fish)
2. Liver converts vitamin D to 25(OH)-vitamin-D (cholecalciferol)
3. Parathyroid hormone acts on kidneys to convert 25(OH)-vitamin-D (cholecalciferol) to 1,25(OH)-vitamin-D (calcitriol)

(calcitriol is active version of vitamin D)

Question 5

What are the symptoms of acute hypercalcaemia?

Answer 5

Dehyrdation
Confusion
Polyuria
Weakness

Question 6

What are the ECG findings in hypercalaemia?

Answer 6

Shortened QT interval

Arrhythmia

Question 7

What are the symptoms are chronic hypercalcaemia?

Answer 7

“stones, bones and psychic mones”

Abdominal pain (renal stones)
Bone pain (ostepenia)
Depression

Question 8

What is primary hyperparathyroidism?

Answer 8

Overactive parathyroid gland producing excess PTH

Question 9

Blood results show:

• Serum Ca: high
• Urinary Ca: normal
• PTH: high
• ALP: normal
• Albumin: normal/low
• Urea: normal/low

Diagnosis?

Answer 9

Primary hyperparathyroidism

Question 10

What is the treatment of primary hyperparathyroidism?

Answer 10

Usually nothing (incidental)

Parathyroidectomy
if organ dysfunction, young or have very high calcium (>2.85)

Question 11

What is secondary hyperparathyroidism?

Answer 11

Physiological production of PTH in response to hypocalcaemia.

Question 12

Blood results show:

• Serum Ca: low
• Urinary Ca: normal
• PTH: high
• ALP: normal
• Albumin: normal
• Urea: normal

Diagnosis?

Answer 12

Secondary hyperparathyroidism

Question 13

What is tertiary hyperparathyroidism?

Answer 13

Autonomous parathyroid gland occuring after long standing secondary hyperparathyroidism due to chronic hypocalaemia

Question 14

What can cause tertiary hyperparathyroidism?

Answer 14

Chronic kidney disease

Loss of renal activation of calictriol results chronic hypocalaemia which causes secondary hyperparathyroidism. This causes parathyroid hyperplasia which can progress to tertiary hyperparathyroidism if not treated

Question 15

How can malignancy cause hypercalcaemia?

Answer 15

Metastatic bone destruction (releases calcium from bones into blood)

Paraneoplasitc production of PTHrp

Osteoclast activating tumours

Question 16

What would your next step in management be if a patients blood results showed:

• Serum Ca: high
• Urinary Ca: normal
• PTH: low
• ALP: high
• Albumin: normal
• Urea: normal

Answer 16

Imaging to find tumour

Blood results suggest malignant hypercalcaemia

Question 17

What is familial hypocalcuric hypercalcaemia?

Answer 17

Autosomal dominant condition affecting the calcium sensing receptor causing asymptomatic hypercalcaemia.

Question 18

Blood results show

• Serum Ca: high
• Urinary Ca: normal
• PTH: high
• ALP: normal
• Albumin: normal
• Urea: normal

Diagnosis?

Answer 18

Familial hypocalcuric hypercalcaemia

Question 19

Thiazide or loop diuretics cause hypercalcaemia?

Answer 19

Thiazide diuretics cause hypercalcaemia

Question 20

Blood results show:

• Serum Ca: high
• Urinary Ca: normal
• PTH: normal
• ALP: normal
• Albumin: high
• Urea: high

Diagnosis?

Answer 20

Dehydration

Question 21

What are the symptoms of hypocalcaemia?

Answer 21

Cramps
Weakness
Paresthesia

Question 22

What is hypoparathyroidism?

Name 4 causes.

Answer 22

Hypofunction of parathyroid glands resulting in insufficient PTH and hypocalcaemia

Destruction (surgical, autoimmune, chemotherapy)

Parathyoidectomy

DiGeorge syndrome

Hypomagneasaemia

Question 23

Why does hypomagnesaemia cause hypocalcameia?

Answer 23

Mg required for calcium secretion from cells

Question 24

How do you treat hypoparathyroidism?

Answer 24

Calcium, vitamin D (+/- magnesium) supplementation

Question 25

What is pseudohypoparathyroidism?

Answer 25

Low calcium caused by genetic PTH resistance

Question 26

What gene mutation causes pseudohypoparathyroidism?

Answer 26

GNAS1 gene

Question 27

How does pseudohypoparathyroidism present?

Answer 27

Obesity, learning difficulty, brachydatyly, McCune Albright syndrome (abnormal bone fibrosis)

Question 28

Bloods show

• Serum Ca: low
• Urinary Ca: normal
• PTH: low
• ALP: normal
• Albumin: normal
• Urea: normal

Diagnosis?

Answer 28

Hypoparathyroidism

Pseudohypoparathyroidism if phenotype suits e.g. obese, learning difficulties, brachydactyly

Question 29

What is pseudopseudohypoparathyroidism?

Answer 29

Clinically like pseudohyooparathyroidism (obese, learning difficulties, brachydactyly, abnormal bone) but calcium and pTH normal, i.e. no PTH resistance

Question 30

Name 5 causes of vitamin D deficiency.

Answer 30

Poor diet
Lack of sunlight
Malabsoprtion
Renal failure
Iatrogenic (anticonvulsants)

Question 31

How does vitamin D deficiency present?

Answer 31

Bone wasting
Dental caries
Muscle wasting

Question 32

What can vitamin D deficiency cause?

Answer 32

• fractures
• osteopenia
• colonic malignancy

Question 33

Pancreatiitis causes

a) hypercalcaemia
b) hypocalcaemia

Answer 33

b) hypocalcaemia (dying pancreas takes in lots of calcium)