Hypercalcaemia and primary hyperparathyroidism Flashcards
What is 40% of calcium bound to in the plasma
albumin
What regulates the plasma concentration of free calcium
PTH and Vitamin D
Where do the superior parathyroid glands develop from
the fourth branchial pouch
Where do the inferior glands develop form
the 3rd branchial pouch
Where does the thymus develop form
the 3rd pouch
What stimulates the PTH release
a decrease in plasma free calcium levels
What senses changes in plasma free calcium
a specific calcium-sensing receptor on the plasma membrane of the parathyroid cells
How does PTH increase plasma calcium
by stimulating:
bone resorption
intestinal absorption of calcium
Renal reabsorption of calcium
How do we obtain sources of vitamin D
diet and synthesis in the skin in the presence of UV light
What are some of the causes of hypercalcaemia
Malignancy: local resorption of bone caused by metastases
Hyperparathyroidism
Hypervitaminosis D - excess vitamin D
Idiopathic
What is the most common cause of hypercalcaemia in ambulatory patients
hyperparathyroidism
What is familial hypocalciuric hypercalcaemia
an autosomal dominant disorder caused by inactivating mutations in the gene encoding the calcium sensing receptor on the parathyroid cells in the kidneys
What are some less common causes of hypercalcaemia
drugs: lithium (increased secretion of PTH)
thiazide diuretics (lower urinary calcium excretion
Immobility: increased bone resorption
Milk-alkali syndrome - high intake of milk or calcium carbonate
What causes primary hyperparathyroidism
Solitary adenoma
multiple adenomas or 4 gland hyperplasia
Parathyroid carcinoma (rare cause)
What might primary hyperparathyroidism be associated with
MEN1
MEN 2
How might patients present with primary hyperparathyroidism
Most asymptomatic some may have: nausea constipation polydipsia polyuria depression generalised aches and pain (bones, stones, abdominal moans and groans)
What is a common feature of primary hyperparathyrodism
Osteoporosis
What needs to measured in patients with suspected primary hyperparathyroidism
phosphate levels - they may be low or low-normal
What conditions should be excluded in patients with suppressed PTH
myeloma
malignancy
granulomatous conditions e.g. TB sarcoidosis and lymphoma
What type of imaging should be performed in patients with confirmed primary hyperparathyroidism
renal US to look for renal calculi
What is the only curative treatment for primary hyperparathyroidism
surgery
What are the indications for surgery for primary hyperparathyroidism
symptomatic patients
asymptomatic patients with:
Why might a total parathyroidiectomy be performed in patients with MEN1
High recurrence rate
What should be given to patients with primary hyperparathyroidism with osteopenia or osteoporosis who are not candidates for surgery
bosphosphonates
What is the most common cause of hypercalcaemia among hospitalised patients
malignancy
