Bone physiology & disorders Flashcards
(44 cards)
What is involved in calcium homeostasis?
Diet
Gut absorption
Vitamin D
Parathyroid hormone
What changes to gut absorption can affect calcium homeostasis?
Bowel pathology
Age
Hormones (pregnancy & lactation)
What changes to parathyroid hormone can affect calcium homeostasis?
Hyperparathyroidism
Hypoparathyroidism
Malignant hypercalcaemia (parathyroid hormone related protein)
What changes to vitamin D can affect calcium metabolism?
Diet Kidney problems Liver problems UVB exposure Drugs
Describe calcium homeostasis
When calcium binds to the calcium sensing receptors on the parathyroid glands it suppresses the secretion of parathyroid hormone
Low calcium >
Parathyroid hormone is secreted >
Parathyroid hormone acts on the bones and kidneys >
Parathyroid hormone stimulates bone reabsorption, calcium reabsorption in the kidney and absorption in the small intestine via vit D synthesis in the kidney
What effect does low vitamin D have on parathyroid hormone levels?
It causes them to increase
Describe vitamin D metabolism
Dehydrocholesterol > sunlight
Cholecalciferol (D3) > liver
25 OH vit D > kidneys
1,25 OH vit D > effects on gut and kidney absorption of calcium and increase in bone density
What are the acute and chronic symptoms of hypercalcaemia?
Acute - thirst, dehydration, confusion, polyuria
Chronic - myopathy, osteopenia, fractures, depression, hypertension, abdominal pain, constipation
In hypercalcaemia what are the possible causes of abdominal pain?
Pancreatitis
Ulcers
Renal stones
What is the phrase used to remember symptoms of hypercalcaemia?
Stones, groans, bones and psychic moans
Which investigations are indicated in syspected hypercalcaemia?
Calcium Albumin Parathyroid hormone Phosphate Urine calcium
What would raised albumin and urea indicate?
Dehydration
What would raised albumin and normal urea indicate?
Cuffed blood sample
What would normal/low albumin, low PTH and high phosphate indicated?
Bone pathology
What would normal/low albumin, high PTH, low/normal phosphate and high urine calcium indicate?
Primary/tertiary hyperparathyroidism
What would normal/low albumin, high PTH, low/normal phosphate and low urine calcium indicate?
Familial hypocalciuric hypercalcaemia
Which test can you use to further assess bone pathology?
Alkaline phosphate
What does high alkaline phosphate in the context of the other investigations indicate?
Bone metastases
Sarcoidosis
Thyrotoxicosis
What does low alkaline phosphate in the context of the other investigations indicate?
Myeloma
Vitamin D excess
Mild alkaline syndrome (thyrotoxicosis, sarcoidosis & raised bicarbonate)
List some causes of hypercalcaemia?
Primary hyperparathyroidism Malignancy Familial hypocalciuric hypercalcaemia Vitamin D Thiazide diuretics Granulomatous disease (sarcoid, TB) Turnover (bedridden, thyrotoxic, Paget's) Tertiary hyperparathyroidism/end stage renal disease
What investigations are indicated in primary hyperparathyroidism and what do they show?
Serum calcium (raised) Serum PTH (raised/normal) Urine calcium (raised)
How can malignancy cause hypercalcaemia?
Metastases
PTH related peptide (paraneoplastic)
Osteoclast activating factors
How can hypercalcaemia from malignancy be investigated?
Calcium (raised)
Alkaline phosphate (raised)
Imaging (x-ray, CT, MRI)
Isotope bone scan
How is acute hypercalcaemia treated?
Fluids (0.9% saline 4-6L) Loop diuretics once rehydrated Biphosphonates Steroids (occasionally for inflammation) Chemotherapy (malignant disease)
