Calcium

Question 1

What is the normal range of plasma calcium?

Answer 1

2.2-2.6mmol/l

Question 2

What percentage of plasma calcium is bound to albumin?

Answer 2

50%

Question 3

Name the two main hormones involved in calcium metabolism

Answer 3

Parathyroid hormone (PTH), calcitriol (1,25-dihydroxy vitamin D2)

Question 4

State the four effects of PTH

Answer 4

Increases renal tubular 1alpha hydroxylation of vitamin D, mobilises calcium from bone, increases renal calcium absorption, increases renal phosphate excretion

Question 5

State the two main effects of calcitriol

Answer 5

Increases calcium and phosphate absorption from the gut, bone remodelling

Question 6

What is primary hyperparathyroidism?

Answer 6

Increased PTH - usually from parathyroid adenoma

Question 7

Describe the blood results in primary hyperparathyroidism

Answer 7

Increased calcium, decreased phosphate, increased or inappropriately normal PTH, increased or normal alkaline phosphatase, normal vitamin D

Question 8

What is secondary hyperparathyroidism?

Answer 8

Renal osteodystrophy

Question 9

Describe the blood results in secondary hyperparathyroidism

Answer 9

Decreased or normal calcium, increased phosphate, increased PTH, increased alkaline phosphatase, normal vitamin D

Question 10

What is tertiary hypoparathyroidism?

Answer 10

Autonomous PTH secretion post-renal transplant

Question 11

Describe the blood results in tertiary hyperparathyroidism

Answer 11

Increased calcium, decreased phosphate, increased PTH, increased or normal alkaline phosphatase, normal vitamin D

Question 12

State two causes of hypoparathyroidism

Answer 12

DiGeorge syndrome, post-thyroid surgery

Question 13

Describe the blood results in hypoparathyroidism

Answer 13

Decreased calcium, increased phosphate, decreased PTH, decreased or normal alkaline phosphatase, normal vitamin D

Question 14

Describe the blood results in vitamin D deficiency

Answer 14

Low calcium, low phosphate, increased PTH, increased alkaline phosphatase, low vitamin D

Question 15

Describe the blood results in Paget’s disease of bone

Answer 15

Normal calcium, normal phosphate, normal PTH, increased alkaline phosphatase, normal vitamin D

Question 16

Describe the blood results in osteoporosis

Answer 16

All normal

Question 17

Describe the symptoms of hypercalcaemia

Answer 17

Renal stones, abdominal pain, psychiatric disturbance, bone pain, polyuria, muscle weakness

Question 18

What is the main cause of hypercalcaemia with increased albumin and urea?

Answer 18

Dehydration

Question 19

What is the underlying cause of hypercalcaemia with low phosphate and low or normal albumin?

Answer 19

Primary or tertiary hyperparathyroidism

Question 20

Name three causes of hypercalcaemia with low albumin, high phosphate, and increased ALP

Answer 20

Bone metastases, thyrotoxicosis, sarcoidosis

Question 21

Name three causes of hypercalcaemia with low albumin, high phosphate, and normal ALP

Answer 21

Myeloma, excess vitamin D, sarcoidosis, milk alkali syndrome

Question 22

State four causes of hypocalcaemia with hyperphosphataemia

Answer 22

Chronic kidney disease, hypoparathyroidism, pseudohypoparathyroidism, hypomagnesaemia

Question 23

State four causes of hypocalcaemia with normal or low phosphate

Answer 23

Osteomalacia, acute pancreatitis, overhydration, respiratory alkalosis

Question 24

Describe the clinical features of hypocalcaemia

Answer 24

Perioral paraesthesia, carpopedal spasm, neuromuscular excitability, Trousseau’s and Chvostek’s signs

Question 25

What is the treatment for hypocalcaemia?

Answer 25

Oral calcium or 10% calcium gluconate IV | If chronic kidney disease: alfacalcidol

Question 26

State five risk factors for renal stones

Answer 26

Dehydration, abnormal urine pH (e.g. high meat intake, renal tubular acidosis), increased excretion of stone constituents, urine infection, anatomical abnormalities

Question 27

State the five most common types of renal stones

Answer 27

Mixed calcium (45%), calcium oxalate (35%), struvite (triple phosphate, 10%), uric acid (5%), cysteine (1-2%)

Question 28

State four radio-opaque renal stones

Answer 28

Mixed calcium, calcium oxalate, struvite, calcium phosphate

Question 29

State two radio-lucent renal stones

Answer 29

Uric acid, cysteine

Question 30

What investigations should be performed for recurrent renal stones?

Answer 30

Serum creatinine, calcium, phosphate, urate, PTH Stone analysis Urine sample for pH, MC&S, amino acids, albumin 24h urine volume, calcium, oxalate, citrate, urate