Calcium 2 (revision Flashcards
What is measured when calcium is measured in the blood?
Free ionised calcium (50 percent)
Bound calcium (to albumin, about 40 percent)
Calcium bound to other ions
Why do we measure corrected calcium?
Sometimes, the serum calcium can appear abnormally low if the albumin goes low, for example in really unwell patients in ITU.
How do you calculate corrected calcium?
Serum calcium ADD 0.02 x (40-albumin)
Calculate the corrected calcium if albumin is 30 and serum calcium is 2.2.
2.2 ADD 0.02 x (40-30) = 2.2 MINUS 0.02 x (10) = 2.2 ADD 0.2 = 2.4.
This means that although the bound calcium is low due to low albumin, the ionised calcium is normal.
2.2 is on the lower end.
What type of calcium needs to be fixed?
Ionised aka free calcium needs to be strictly maintained
What three types of parathyroid stuff can cause hyperparathyroidism?
Adenoma
Hyperplasia
MEN 1
What is the first question to ask if you suspect hypercalcemia?
is the PTH also high?
If the PTH is low and calcium is high, what are the differentials?
Cancer
Sarcoidosis
Milk alkali syndrome (too many Rennies)
VIT D excess
THYROTOXICOSIS
If the PTH is high and the calcium is high, what are your differentials?
Primary hyperparathyroidism
Familial hypocalciuric hypercalcemia
Hypocalcemia causes
PTH causes:
Post parathyroidectomy
Autoimmune hypoparathyroidism
Di George syndrome - congenital lack of parathyroid hormones
Magnesium deficiency
Non-PTH causes:
Renal failure/CKD
VIT D deficiency + all causes of that
PTH resistance (pseudohypoparathyroidism)
Symptoms of HYPOcalcemia
CONVULSIONS aka epileptic fits (v v bad)
Chvostek’s twitch
Trousseau’s spasm due to high albumin and even lower calcium temporarily during the blood pressure cuff tightening
Parathesias
Arrhythmias
Three mechanisms by which malignancy causes hypercalcemia
Humoral hypercalcemia - PTHrP - e.g. released by small cell lung cancer
Haematological malignancy - cytokines - released by myelomas
Bone mets - osteolysis - e.g. breast cancer
