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
