Clinical calcium homeostasis Flashcards
Dietary sources of calcium
fish where you eat the bones eg sardines milk, cheese, dairy products tofu green leafy veg (not spinach) soy beans bread nuts
4 functions of calcium
neurotransmitter release
bone formation
muscle contraction
cell division and growth
What is important to remember when measuring a patient’s calcium?
FREE calcium in blood
need to consider albumin levels
Sources of vitamin D
sunlight
fortified cereals and fat spread
oily fish
eggs
What cells in the parathyroid respond directly to changes in calcium concentration?
chief cells
What are the receptors which help the parathyroid gland sense changes in calcium concentration?
calcium sensing receptor
Is PTH secreted in response to high or low plasma calcium?
low
Effects of PTH
direct = bone and renal tubule reabsorption
mediates renal conversion to active vitamin D
What 2 organs play a role in calcitriol metabolism?
liver
kidneys
Why do some people require supplements with the already active vitamin D?
renal failure
Acute neuromuscular symptoms of hypocalcaemia
muscle twitching paraesthesia chovstek's sign Troussea's sign seizures laryngospasm and bronchospasm
Acute cardiac symptoms of hypocalcaemia
prolonged QT interval arrhythmia heart failure hypotension papilloedema
Chronic signs/symptoms of hypocalcaemia
ectopic calcification eg basal ganglia parkinsonism dementia dry skin abnormal dentition
Explain Chovstek’s sign
patient relaxes facial nerve and sat to the side of us
tap facial nerve anteriorly to ear
lip twitch –> all facial muscles spasm
Explain Trosseau’s sign
Blood pressure cuff around arm and pumped up to just past systolic pressure and left for 2-3 mins
as deflating the arm curves inwards and carpal spasm
Causes of hypocalcaemia
disruption of parathyroid gland due to total thyroidectomy (temporary or permanent effects) selective parathyroidectomy severe vitamin D deficiency Magnesium deficiency (PPI) cytotoxic drug induced hypocalcaemia pancreatitis, blood transfusion
Low PTH hypoparathyroidism causes
genetic post surgical autoimmune infiltration HIV radiation induced hungry bone syndrome
High PTH (secondary hyperparathyroidism) causes of low calcium
vitamin D deficiency pseudohypoparathyroidism renal disease acute pancreatitis hypomagnesemia
Drugs which can cause hypocalcaemia
cinacalcet
inhibitors of bone resorption eg bisphosphonates
fluoride poisoning
phenytoin
Clues important in the diagnosis of hypocalcaemia
symptoms, vit D and calcium intake, neck surgery, FH, autoimmune, medication
neck surgery scars
Investigations for hypocalcaemia
ECG, serum calcium, albumin, phosphate, PTH, U+E’s, vitamin D, magnesium
If PTH is low/normal what can the causes of hypocalcaemia be?
magnesium deficiency
primary hypoparathyroidism or CSR defects
If PTH is high what can the causes of hypocalcaemia be?
vitamin D deficiency
renal failure
pseudohypoparathyroidism
calcium deficiency
5 causes of hypoparathyroidism
surgery/ autoimmune - destruction agenesis infiltration reduced PTH secretion resistance to PTH
When does pseudohypoparathyroidism present?
childhood
What is pseudohypoparathyroidism?
target organ - kidney, bone
unresponsive to PTH
3 classic characteristics of pseudohypoparathyroidism
hypocalcaemia
increased PTH
hyperphosphatemia
Characteristics of AHO
obesity, short stature, shortening of 4th and 5th metacarpal bones
What is shortening of 4th and 5ht metacarpal bones characteristic of?
AHO
pseudohypoparathyroidism
What is AHO without PTH or calcium abnormalities called?
pseudopseudohypoparathyroidism
Treatment for mild hypocalcaemia
oral calcium tablets
vitamin D
stop precipitating magnesium deficiency and replace
Treatment for severe hypocalcaemia
medical emergency
IV calcium gluconate
treat underlying cause
2 hydroxylated forms of vitamin D
calcitriol
alfacalcidal
Causes of hypercalcaemia
malignancy
primary hyperparathyroidism
MEN, vitamin D intoxication, FHH, thiazide diuretics, lithium, acromegaly
Saying for hypercalcaemia
stones, bones, groans and psychic moans
Clinical features of hypercalcaemia A - Renal B - GI C - CVS D - neurological E - MSK
A - nephrolithiasis, polyuria, polydipsia
B - abdominal pain, constipation, anorexia, nausea and vomiting, pancreatitis, peptic ulcer, biliary calculi
C - short QT interval, bradycardia, hypertension
D - depression, reduced concentration, fatigue, confusion
E - osteopenia/osteoporosis, bone pain
Clues in diagnosis of hypercalcaemia
symptoms, FHH, medications, systemic enquiry
lymph nodes, malignancy eg breast , lung
Investigations for hypercalcaemia
U+E, calcium, phosphate, myeloma screen, serum ACE, PTH, ECG
PTH high or normal hypercalcaemia cause
primary hyperparathyroidism
PTH low hypercalcaemia
malignancy
drug causes
Primary hyperparathyroidism epidemiology
female, 50-60, asymptomatic
few linked to lithium or neck irradiation
Most common cause of primary hyperparathyroidism
parathyroid adenoma
can also have 4 gland hyperplasia but MEN and carcinoma are rare
Investigations for primary hyperparathyroidism
calcium, PTH U+E, vitamin D abdominal imaging - renal calculi DEXA scan 24 hour urine collection for calcium to exclude FHH SESTAMIBI ultrasound
5 indications for parathyroid surgery
under 50 calcium more than 0.25mmol raised eGFR <60 or renal calculi osteoporosis - DEXA symptomatic
2 medical management of hypercalcaemia
fluids
cinacalcet - calcimetic
What does cincalcet do?
lead to fall in PTH by acting like calcium and therefore decrease calcium
Inheritance of FHH and what has gone wrong
autosomal dominant
CSR
Examples of malignancy leading to hypercalcaemia
squamous cell eg lung, cervix
breast, multiple myeloma, lymphoma
MEN type 1
primary hyperparathyroidism
pituitary
pancreatic
MEN type 2A
medullary thyroid cancer
phaeochromocytoma
hyperparathyroidism
Why is family history important in hyperparathyroidism?
MEN
FHH
2 primary management of hypercalcaemia
rehydration
IV bisphosphonates
second line management
List some second line managements in hypercalcaemia
glucocorticoids
calcitonin
calcimetics
parathyroidectomy
