Hyper & Hypoparathyroidism

Question 1

How many parathyroid glands are there? Where are they located?

Answer 1

4 parathyroid glands, situated in 4 corners of the thyroid gland.

Question 2

What is the role of the parathyroid glands?

Answer 2

Chief cells of parathyroid glands produce PTH in response to hypocalcaemia.

Question 3

Via what 3 ways does PTH increase calcium levels?

Answer 3

1) Increasing osteoclast activity in bones (reabsorbing calcium from bones)

2) Increasing calcium reabsorption in the kidneys (less calcium is lost in urine)

3) Increasing vitamin D activity (converts it into its active form), resulting in increased calcium absorption in the intestines

Question 4

Vitamin D & calcium?

Answer 4

Vitamin D acts to increase calcium absorption from the intestines.

Question 5

What is the most common cause of hypercalcaemia in outpatients?

Answer 5

1ary hyperparathyroidism

Question 6

1ary vs 2ary hyperparathyroidism?

Answer 6

1ary –> caused by uncontrolled PTH production by a tumour of the parathyroid gland.

2ary –> insufficient vitamin D or CKD reduces calcium absorption from the intestines, kidneys and bones –> hypocalcaemia –> raised PTH

Question 7

What is 3ary hyperparathyroidism?

Answer 7

When 2ary hyperparathyroidism continues for an extended period, after which the underlying cause is treated.

Hyperplasia of the parathyroid glands occurs as they adapt to producing a higher baseline level of PTH.

When the underlying cause of the secondary hyperparathyroidism is treated, the baseline parathyroid hormone production remains inappropriately high.

Question 8

What is the most common cause of 1ary hyperparathyroidism?

Answer 8

Solitary parathyroid adenoma

Question 9

What inherited condition can cause 1ary hyperparathyroidism?

Answer 9

Multiple endocrine neoplasia (MEN)

Question 10

What happens in the 1ary hyperparathyroidism?

Answer 10

A region of cells within the parathyroid glands cease to respond to this negative feedback loop.

These cells continuously secrete PTH irrespective of the serum calcium concentration.

This results in hypercalcaemia.

Question 11

Symptoms of hypercalcaemia?

Answer 11

‘Stones’ - increased risk of kidney stones

‘Bones’:
- Bone pain
- Osteopenia and osteoporosis

‘Abdo groans’:
- Abdominal pain
- Constipation
- N&V

‘Psychiatric moans’
- Fatigue
- Depression
- Memory impairment

Also polyuria, paraesthesia & muscle cramps.

Question 12

What should be excluded in all patients with hypercalcaemia?

Answer 12

Malignancy

Question 13

What are the 2 main mechanisms of hypercalcaemia of malignancy?

Answer 13

1) PTHrP secreting tumours (e.g. lung, breast and kidney)

2) Osteolytic lesions (e.g. bone metastasis and multiple myeloma)

Question 14

Serum PTH in hypercalcaemia of malignancy?

Answer 14

Low

Question 15

What is familial hypocalciuric hypercalcaemia (FHH)?

Answer 15

A rare autosomal domination condition in which there is reduced renal excretion of calcium

Question 16

What test can be used to differentiate between hyperparathyroidism & FHH?

Answer 16

24-hour urinary calcium:

• FHH results in a hypocalciuria
• 1ary hyperparathyroidism results in high or normal urinary calcium

Question 17

Interpret results:

• High PTH
• High calcium

Answer 17

1ary hyperparathyroidism –> tumour

OR

3ary hyperparathyroidism –> hyperplasia

Question 18

Interpret results:

• High PTH
• Low/normal calcium

Answer 18

2ary hyperparathyroidism –> Low vitamin D or CKD

Question 19

Most common 1st line mx of 1ary hyperparathyroidism?

Answer 19

Parathyroidectomy

Question 20

If surgery is not possible, what are some mx options for symptomatic hypercalcaemia in 1ary hyperparathyroidism?

Answer 20

1) Calcitonin

2) Cinacalcet

3) Bisphosphonates

Question 21

How does calcitonin reduce serum calcium levels?

Answer 21

By inhibiting bone and kidney resorption of calcium

Question 22

What are some complications of untreated hypercalcaemia?

Answer 22

1) Osteoporosis and fragility fractures

2) Kidney stones and kidney injury

3) HTN & heart disease

4) GI disorders e.g. peptic ulcer disease, pancreatitis and gallstones

Question 23

What are some procedure specific complications that can arise following a parathyroidectomy? (2)

Answer 23

1) Damage to the recurrent or superior laryngeal nerves

2) Post operative hypocalcaemia can result after the removal of too much parathyroid tissue

Question 24

How does increased PTH affect phosphate?

Answer 24

Causes LOW phosphate levels

Question 25

What is hypoparathyroidism?

Answer 25

Deficient or absent PTH production –> low levels of calcium and high levels of phosphate in the blood.

Question 26

What is the most common cause of hypoparathyroidism?

Answer 26

Damage or removal of the parathyroid glands during neck surgery, especially thyroidectomy.

Question 27

What genetic disorder can result in hypoparathyroidism?

Answer 27

DiGeorge syndrome

Question 28

What is the hallmark feature of hypoparathyroidism?

Answer 28

Hypocalcaemia –> presents with neuromuscular irritability

• mild numbness or tingling of the extremities and around the mouth
• muscle cramps
• fatigue
• tetany
• carpopedal spasm
• laryngospasm
• seizures

Question 29

What 2 signs may be elicited in hypocalcaemia?

Answer 29

1) Chvostek’s sign

2) Trousseau’s sign

Question 30

What is Trousseau’s sign?

Answer 30

carpopedal spasm induced by occluding the brachial artery with a blood pressure cuff

Question 31

What is Chvostek’s sign?

Answer 31

Twitching of the facial muscles in response to tapping over the facial nerve

Question 32

What may ECG show in hypocalcaemia?

Answer 32

Prolonged QT interval

Question 33

Mx of hypoparathyroidism?

Answer 33

1) Oral calcium & active vitamin D analogues e.g. calcitriol or alfacalcidol

2) Diet - high-calcium, low-phosphorus diet