Chempath: Clinical chemistry

Question 1

What happens when K levels are altered?

Answer 1

MYOCARDIAL INSTABILITY
Low K+
- Ventricular fibrilation

High K+

• Asystole
• Chest pain, palpitations
• Tiredness, weakness

Question 2

What happens when Ca levels are altered?

Answer 2

NERVE TRANSMISSION ISSUES

Low Ca2+

• Tetany
• Arrhythmia
• Convulsions

High Ca2+

• Stones (renal) = calcium oxalate
• Bones = osteoporosis, osteopaenia
• Moans (abdominal) = N+V, constipation, pancreatitis
• Groans (psychic) = delirium/ altered mental state

Question 3

What are the hormones that raise Ca? reduce calcium?

Answer 3

PTH
Calcitriol (activated vitamin D)(1,25-(OH)2D3)

Calcitonin - reduces ca

Question 4

How is PTH, Calcitonin and Calcitriol produced?

Answer 4

PTH (parathyroid glands)

Calcitonin (parafollicular cells)

Calcitriol (activated vitamin D) (skin + UV light)

Question 5

What effect does PTH have on:
Kidneys
Bone
Small intestines

Overall impact?

Answer 5

Kidneys:

• 1α-hydroxylase stimulation (stimulates calcitriol)
• Increased calcium reabsorption
• Increased phosphate excretion

Bone:
Increased bone resorption

Small intestines:
Increased calcium absorption
Increased phosphate absorption (small effect)

Overall = ↑ Calcium, ↓↓ Phosphate

Question 6

What effect does Calcitriol have on:
Kidneys
Bone
Small intestines

Overall impact?

Answer 6

Kidneys:

• Increased calcium reabsorption
• Increased phosphate excretion

Bone:
Increased bone formation (minor effect)

Small intestines:
Increased calcium absorption
Increased phosphate absorption (small effect)

Overall = ↑↑ Calcium, ↓ Phosphate

Question 7

What condition cause cause pepper pot skull?

Answer 7

Hypercalcaemia - lytic leisons can also get osteitis fibrosa cystica

Question 8

Mx of hypercalcaemia?

Answer 8

> 3mmol
Fluids, Fluids, fluids !!!

Can also give furesomide to cause clacuresis

If resistant (suggests malignancy) –> IV pamidronate / zoledronate (bisphosphonates)

<3mmol
Keep hydrated can be oral or IV fluids

Question 9

What medication should be avoided in hypercalcaemic pts?

Answer 9

THIAZIDES - can cause Ca retention

Question 10

1. Which hormone decreases blood calcium levels?

Answer 10

Calcitonin

Question 11

2. Which biomarker can be used to confirm medullary thyroid cancer (e.g. in MEN2 syndrome)?

Answer 11

Calcitonin - LEARN THIS

Question 12

3. Which enzyme does PTH activate in the kidneys?

Answer 12

1 alpha-hydroxylase

Question 13

4. Which hormone increases urinary phosphate excretion?

Answer 13

PTH (phosphate trashing hormone)

Question 14

The clinical features of hypercalcaemia include which one of the following?

Polyuria and polydipsia
Tetany
Hypotension
Diarrhoea
Easy bruising

Answer 14

Polyuria and polydipsia

“Stones, bones, abdominal moans, psychiatric groans”

Tetany - sign of HYPOcalcaemia

Question 15

A 75 year old woman presents with polyuria, constipation and her mood has been low over the past few weeks. Her PMHx includes hypertension, CKD, and ischaemic heart disease. Her blood results are included.

High = Ca, PO4-, PTH

What is the most likely diagnosis?

Malignancy
Primary hyperparathyroidism
Secondary hyperparathyroidism
Tertiary hyperparathyroidism
Hyperthyroidism

Answer 15

Tertiary hyperparathyroidism - EVERYTHING IS HIGH

Question 16

A 75 year old woman presents with polyuria, constipation and her mood has been low over the past few weeks. Her PMHx includes hypertension and ischaemic heart disease. Her blood results are included.

↑ calcium, ↓ phosphate, ↔ PTH

What is the most likely diagnosis?

Malignancy
Primary hyperparathyroidism
Secondary hyperparathyroidism
Tertiary hyperparathyroidism
Hyperthyroidism

Answer 16

Primary hyperparathyroidism - INAPPROPRIATELY NORMAL PTH!!!