Chem Path: Calcium metabolism
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What is normal calcium serum levels?
2.2 to 2.6
What is corrected calcium and what is the formula?
It is corrected for albumin levels It tells you what calcium would have been if albumin is normal serum calcium + 0.02(40-serum albumin)
What are the 3 actions of PTH
Turn on osteoclasts to break down bone Increased renal calcium reabsorption Increases 1 alpha hydroxylation of vit D and vit D causes calcium reabsorption in the gut
What is PTH’s effect on phosphate
Increases phosphate excretion in kidneys
How is Vit D processed in the body?
Cholecalciferol is 25 hydroxylased in the liver, and is 1 alpha hydrxylased in the kidneys
What are ergocalciferol and cholecalciferol
Ergo is plant product Chole is animal product
Other than the kidney, what else can produce 1 alpha hydroxylase
Sarcoid lung tissue
How does Vit D affect phosphate?
It causes phosphate reabsorption in gut
What does Vit D deficiency cause?
Osteomalacia in adults Rickets in kids
How does osteomalacia present?
Loosers zone and pseudo fractures
What is the biochem of osteomalacia
Low calcium, low phosphate and high ALP
What medication can cause low Vit D?
Anti convulsants
What is PTHrp
Produced by placenta to steal calcium from mother. Also expressed in cancer patients
What is the biochem of osteoporosis
All normal levels
What are t and z scores in DEXA scan
T score compared to young people - below 2.5 is osteoporosis z score compared to your age
What drugs to treat osteoporosis
Bisphosphonates - alendronate - take them alone Teriparatide - PTH analogue Strontium SERM - Raloxifene and tamoxifen (antagonist in breast but agonist in bone and uterus)
What are symptoms of hypercalcaemia?
Polyuria, polydipsia, constipation, confusion, seizure, coma
What can cause primary hyperparathyroidism
Prarathyroid adenoma Hyperplasia due to MEN1
What are the features of primary parathyroidism
Bones, stones, moans, groans
What is FHH/FBH
Raised calcium levels due to mutation in CaSR. Higher threshold for PTH release
What drug causes increased PTH and increased calcium
Lithium
What are some non PTH driven causes of hypercalcaemia
Sarcoidosis, thyrotoxicosis, hypoadrenalism, thiazide diuretics
Acute management for hypercalcaemia?
Fluids - 0.9% saline - 1L over an hour or 500ml per hour
How does hypocalcaemia present?
Troussoue’s sign - carpals spam when measuring bp Chovstek’s sign - increased muscle excitability