T1 L21: Diagnostic biochemistry of calcium and bone disorders Flashcards
Which 2 molecules regulate calcium?
activated vitamin D and Parathyroid hormone (PTH)
Fall in which ion triggers release of PTH?
Calcium
What is parathyroid related peptide?
A peptide released by a variety of tumours and can cause hypercalcaemia
How is vitamin D produced?
UV light and from diet
What is calcitonin?
Reduces bone resorption and protects the skeleton during stresses like growth and pregnancy
What is FGF-23?
It’s secreted by osteocytes, osteoblasts, and osteoclasts in response to serum phosphate. It reduces phosphate reabsorption in the renal proximal tubule
May be important in renal bone disease
What are the 2 categories of hypercalcaemia cause?
Non-parathyroid: malignancy, vitamin D excess, sarcoidosis
Parathyroid hormone cause: primary and tertiary hyperthyroidism, calcium receptor defects
What are the 2 main categories of hypocalcaemia cause?
Non-parathyroid: vitamin D deficiency/malabsorption, renal failure, PTH receptor defects
Parathyroid: Hypoparathyroidism caused by surgery/radiotherapy or congenital, Mg deficiency
What is familial hypocalciuric hypercalcaemia?
An inherited disorder that causes abnormally high levels of calcium in the blood (hypercalcemia) and low to moderate levels of calcium in urine (hypocalciuric)
What is pseudohypoparathyroidism?
The body fails to respond to parathyroid hormone
People present with biochemistry of hyperparathyroidism but the PTH levels are high
What is Albright’s hereditary Osteodystrophy?
A syndrome associated with Pseoduhypoparathyroidism
Clinical presentation: Short stature, shortened 4th and 5th metacarpals, round facies, obesity, sometime mild mental retardation
What are the 2 different phenotypes of pseudoparathyroidism?
It’s an example of genetic imprinting
If mutant gene is inherited from mother then biochemical and physical features manifest
If mutant gene is inherited from father, pseodopseudoparathyroidism manifests that only causes physical features
Because only maternal gene is predominantly expressed in the renal tubule
What is Paget’s syndrome?
Causes dysregulated bone growth (immobilisation hypercalcaemia)
What is calcium alkali syndrome?
It’s the third most common cause of hypercalcaemia
It’s characterized by elevated blood calcium levels, metabolic alkalosis, and acute kidney injury
