Chempath 20: Clinical Chemistry CPC Flashcards
What happens when you fall on an outstretched hand
Colles fracture
Radius fractures backwards away from the palm side
What fracture is caused by falling on a flexed wrist ?
Smith’s fracture
List 3 causes of hypercalcaemia?
Primary hyperparathyroidism
Cancer
Sarcoidosis
How can you differentiate Primary hyperparathyroidism from cancer causing hypercalcaemia?
Plasma PTH
0 in cancer and high in primary hyperparathyroidism
What is PTHrP ?
Give 2 locations where its produced ?
PTH related peptide
Produced by the placenta (so mothers calcium increases and baby can steal some)
produced by breast and secreted into breast milk
Why is PTHrP activation in cancer a bad prognostic feature ?
PTHrP stimulates cancer invasion of bone by turning on osteoclasts.
Which enzyme activates Vitamin D in the kidneys ?
1-alpha hydroxylase
How does vitamin D affect the kidneys ?
Activated vitamin D (calcitriol) causes increased reabsorption of calcium
Which tumours are featured in MEN1 ?
Pituitary tumour
Parathyroid tumour
Pancreas - islet cell tumour
What symptoms do you get with hypercalcaemia ?
Moans- depression, psychosis, coma
Groans- constipation, abdominal pain,
Bones- fractures, bone pain (osteitis fibrosa cystica)
Stones- renal colic (calcium oxalate stones)
Polydipsia and polyuria (nephrogenic diabetes insipidus)
Which organism causes recurrent UTIs in patients with calcium stones ?
Proteus mirabilis
Why are patients so dehydrated with Hypercalcaemia ?
Calcium acts like mannitol, it causes water to move with it into the urine causing a diuresis
How do you treat hypercalcaemia ?
- Saline fluids (to rehydrate), 6L in 24 hrs, first L quickly over 1hr to deal with dehydration
- Furusamide (causes calcium loss in the urine)
- IV pamidronate (a bisphosphonate that stops bone resorption by causing osteoclast apoptosis. Only use in very high calcium)
Why is giving saline to hypercalcaemia patients with liver failure contraindicated ?
What do you give instead ?
They retain salt so can cause hypernatraemia
Dextrose Fluids
Which diuretics should be avoided in hypercalcaemia?
Thiazides
They cause increased calcium reabsorption into the blood.
Which feature of Osteitis fibrosa cystica is described by this histology:
“Multinucleate giant cells in the bone”
Brown tumours
Giant cells are the activated osteoclasts
A lady is noted to have hypercalcaemia, her chest X ray shows bilateral hilar lymphadenopathy.
What is the most likely diagnosis ?
Sarcoidosis
A histology specimen of a patient with hypercalcaemia shows “non-caseating granuloma”.
What is the most likely diagnosis ?
Sarcoidosis
What is the mainstay of treatment for sarcoidosis ?
Steroids
How does sarcoidosis cause Hypercalcaemia ?
- Macrophages in the lungs of people with sarcoidosis express 1-alpha-hydroxylase.
- This causes increased activation of vitamin D (especially in the summer)
- Activated Vitamin D causes increased calcium reabsorption from the kidneys and G.I tract
What are the cardiac effects of hyper and hypokalaemia
Hyperkalaemia - asystole
Hypokalaemia - VF
What are the mechanisms of hypercalcaemia of malignancy
PTHrP
Cancer invading the bone
Describe features of primary hypercalcaemia
Causes efflux of calcium from bone and increased calcium reabsorption in kidney + increased absorption of calcium in the intestines
PTH - activates 1 alpha hydroxylase in kidneys - activates vitamin D - increases absorption of calcium in intestines
Sign of hypercalcaemia
Band keratopathy
Calcium deposition across the front of the eye
Complications of hypercalcaemia
Renal stones
Pancreatitis
Peptic ulcer disease
Skeletal changes - osteitis fibrosa cystica
Management of renal stones
Lithotripsy
Cystoscopy
Lithotomy
Surgery for hyperparathyroidism
Minimally invasive parathyroidectomy
Technetium sestamibi can show a hyperactive parathyroid gland
