14. Parathyroid gland disorders

Question 1

What does the parathyroid gland control?

Answer 1

Serum calcium levels

Question 2

What are the 2 hormones released by the parathyroid gland?

Answer 2

PTH - secreted in response to low serum calcium.

Calcitonin - secreted in response to high serum calcium.

Question 3

Describe the usual function of parathyroid hormone (PTH).

Answer 3

Secreted in response to low ionised calcium levels (-ve feedback).

Acts by increasing osteoclastic activity - releases calcium/phosphate from bones.

1. Increases bone reabsorption
2. Increases calcium reabsorption in kidneys
3. Increases Calcitriol production -> then acts on the intestine to increase calcium absorption
4. Decreases phosphate reabsorption in kidney.

Overall effect = increases calcium, decreases phosphate.

Question 4

Define hypoparathyroidism.

Answer 4

A condition where there is an underproduction of parathyroid hormone

Question 5

Give 3 causes of primary hypoparathyroidism.

Answer 5

1. Autoimmune polyendocrine syndrome type 1 (destroys PT glands)
2. DiGeorge syndrome
3. Autosomal dominant hypoparathyroidism

Question 6

Give 2 causes of secondary hypoparathyroidism.

Answer 6

1. Radiation
2. Surgery
3. Hypomagnesaemia
4. Removal of PT glands

Question 7

What is the affect of hypoparathyroidism on serum calcium levels?

Answer 7

Hypoparathyroidism -> hypocalcaemia.

Question 8

What would biochemical tests show in a patient with hypoparathyroidism?

Answer 8

Low calcium
Low/normal phosphate

Question 9

Give 5 causes of hypocalcaemia.

Answer 9

1. Dietary insufficiency.
2. Anticonvulsant therapy.
3. CKD.
4. Vitamin D deficiency.
5. Osteomalacia.
6. Hypoparathyroidism.

Question 10

Give 2 causes of hypocalcaemia with normal/low phosphate.

Answer 10

1. Osteomalacia
2. Acute pancreatitis
   (FFAs bind to calcium)
3. Over-hydration
4. Respiratory alkalosis

Question 11

Give 2 causes of hypocalcaemia with high phosphate.

Answer 11

1. CKD
   (Chronic kidney disease -> lack of reabsorption)
2. Hypoparathyroidism
3. Acute rhabdomyolysis
   (cells die and release phosphate and binds to calcium and making in insoluble)
4. Vitamin D deficiency
5. Hypomagnesaemia
   (needed for PTH secretion)

Question 12

Give 5 clinical features / signs of hypocalcaemia (hypoparathyroidism)?

Answer 12

SPASMODIC:
Spasms.
Perioral paraesthesiae.
Anxious, irritable, irrational.
Seizures.
Muscle tone increased in smooth muscle - colic, wheeze, dysphagia.
Orientation impaired (time, place and person) and confusion.
Dermatitis.
Impetigo herpetiformis.
Chvostek’s sign, choreasthetosis, cataract, cardiomyopathy.

Question 13

What is Chvostek’s sign and what does it indicate?

Answer 13

When facial nerve is tapped at the angle of the jaw, facial muscles on the same side of the face contract.

-> Indicates nerve hyperexcitability due to hypocalcaemia.

Question 14

What is Trousseau’s sign and what does it indicate?

Answer 14

BP cuff causes wrist to flex and fingers to draw together.

-> Indicates nerve hyperexcitability due to hypocalcaemia.

Question 15

Investigations for hypoparathyroidism / hypocalcaemia.

Answer 15

Hyoparathyroidism -> hypocalcaemia and so:

Bloods
→ low calcium. check PTH, VitD, albumin, phosphorus, magnesium

ECG
1. Small T waves
2. Long QT interval

Question 16

Treatment of hypoparathyroidism.

Answer 16

Treat the hypocalcaemia:

-> Calcium supplements (calcium gluconate):
1. 10ml calcium gluconate/chloride 10% slow IV
2. Oral Calcium

-> Calcitriol (active vitD)

Question 17

Give 2 complications of hypoparathyroidism / hypocalcaemia.

Answer 17

Seizure
Cardiac arrest (decreases heart rate and contractility) - a medical emergency!

Question 18

Define hyperparathyroidism.

Answer 18

A condition where there is an overproduction of parathyroid hormone.

Question 19

Give 2 causes of primary hyperparathyroidism.

Answer 19

1. Solitary parathyroid adenoma
   - ↑PTH ↑Calcium ↓Phosphate
2. Malignancy (lung small cell, breast, renal)
3. Hyperplasia of parathyroid gland.

Question 20

What is the cause of secondary hyperparathyroidism?

Answer 20

Physiological compensatory hypertrophy of the gland in an attempt to correct low serum calcium from renal failure

Question 21

What is the cause of tertiary hyperparathyroidism?

Answer 21

Prolonged uncorrected hypertrophy
I.E. long term hyperparathyroidism

Question 22

What is the affect of hyperparathyroidism on serum calcium levels?

Answer 22

Hyperparathyroidism -> hypercalcaemia

Question 23

Give 3 causes of hypercalcaemia.

Answer 23

1. Primary Hyperparathyroidism.
2. Hypercalcaemia of malignancy.
   -> Secretion of PTHrP (PTH-related protein)
3. Vitamin D toxicity.
4. Myeloma / Lymphoma

Question 24

Give 5 clinical features / symptoms of hyperparathryoidism / hypercalcaemia.

Answer 24

Hyperparathyroidism -> hypercalcaemia:

!!Bones, Stones, Psychic Moans and Abdo Groans!!

1. Bones - pain, cysts, tumours
2. Stones - renal colic, polyuria, nocturia, haematuria, hypertension
3. Psychic moans - depression, psychosis, anxiety, malaise
4. Abdo groans - abdominal pain, nausea, vomiting, constipation, anorexia

Question 25

Investigations of hyperparathyroidism / hypercalcaemia.

Answer 25

Hyperparathyroidism -> hypercalcaemia and so: 1. PTH/bone profile in bloods: -> High calcium; High PTH; Low Phosphate 2. 24h urinary calcium: -> High Calcium excretion 3. ECG: - Tall T waves - Shorted QT interval 4. DEXA scan to show any skeletal involvement 5. Abdo X-ray for renal stones

Question 26

What classical sign is seen on imaging (CT, X-rays) a patient with hyperparathyroidism?

Answer 26

Pepper pot skull - Multiple tiny well-defined lucencies in the calvaria caused by resorption of trabecular bone in hyperparathyroidism

Question 27

Treatment of hypercalcaemia.

Answer 27

1. IV normal saline. 2. IV furosemide. 3. IV calcitonin.

Question 28

Treatment of hyperparathyroidism.

Answer 28

1. Partial/total parathyroidectomy 2. IV saline 3. IV bisphosphonates (alendronate). 4. Cinacalcet - increases sensitivity of parathyroid cells to calcium. 5. Avoid thiazide diuretics 6. Low calcium/vit D diet.

Question 29

From what malignancies do you most commonly get hypercalcaemia?

Answer 29

Squamous cell lung, breast, bone metastasis, myeloma, GI cancer

Question 30

How does hypercalcaemia of malignancy occur in myeloma?

Answer 30

Stimulation of osteoclasts by IL-1 and TNF promotes calcium loss from bones

Question 31

How would you treat hypercalcaemia of malignancy, other than normal malignancy management?

Answer 31

Rehydration. Bisphosphonates - pamidronate (inhibit osteoclast activity)

Question 32

Give 3 symptoms of hypercalcaemia of malignancy

Answer 32

Lethargy Anorexia Nausea Polydipsia Polyuria Constipation Dehydration Confusion Weakness