2 - Calcium Pathology Flashcards
Hyperparathyroidism is a condition of what?
Excess PTH secretion
What two types of hyperparathyroidism are there?
Primary - within parathyroid gland
Secondary - elsewhere i.e. Chronic renal failure / rickets
What is a common cause of primary hyperthyroidism?
Monoclonal parathyroid adenoma (hyperplasia)
What two serum findings result from primary hyperparathyroidism?
1) Hypercalcaemia
2) HYPOphosphataemia
What are 2 complications of primary hyperparathyroidism? (bone/kidney)
Bone demineralisation - loss of calcium and phosphate.
Renal calculi from hypercalciuria - concentrations get so high it comes out of solution.
What are the most common type of calcium kidney stones?
Calcium oxalate
What is a complication of chronic bone demineralisation?
Multiple bone cysts
osteitis fibrosa cystica
What are 3 genetic causes of primary HPT?
1) Vitamin-D receptor mutation
2) MEN1 mutation
3) Over-expression of cyclin D1
What’s the pathophysiology of a vitamin-D receptor mutation leading to Primary HPT?
Vitamin D-R provides negative feedback to parathyroid gland, inhibiting gene expression of PTH.
Mutation = loss of -ve feedback.
What’s the pathophysiology of MEN1 mutation causing primary HPT?
MEN1 is a tumour suppressor gene. Mutation results in neoplasia.
What’s the pathophysiology of cyclin D1 over-expression causing primary HPT?
Cyclin D1 is a cell-cycle regulator.
Overexpression favours cell division = sporadic parathyroid adenoma.
What other symptoms occurs with hyperparathyroidism?
‘Stones, bones, abdominal groans and psychic moans’
Muscle weakness, depression, GI upset, lethargy, aches.
What is tetany?
Muscular spasms, caused by a deficiency in calcium (Parathyroid dysfunction)
What is the treatment for primary HPT?
Surgery - parathyroidectomy
What is the main complication of a parathyroidectomy?
Nephrolithiasis
How do you best avoid nephrolithiasis following a parathyroidectomy?
Hydration
Moderate calcium intake
What scan is used to detect parathyroid tumours?
Sestamibi
What radioactive isotope is used in the sestamibi scan?
Technetium 99
What is the full name of the modern parathyroidectomy?
Minimally invasive radio-guided parathyroidectomy (MIRP)
During the MIRP, how does the surgeon confirm excised tissue is a tumour and that they’ve got it all?
Radiation-sensitive probe can detect the presence of Technetium 99.
What two pathologies occur in the kidney that can augment secondary hyperparathyroidism?
1) Increase phosphate reabsorption (inability to excrete)
2) Decreased 1alpha hydroxylation (less vitamin D)
What 4 factors (2 direct, 2 indirect) therefore, increase the level of PTH secretion?
1) High plasma phosphate
1b) Low free calcium
2) Low vitamin D
2b) Decrease calcium GUT absorption
Chronic renal failure results in what area of the kidney being unresponsive to PTH levels?
Proximal convoluted tubule
In the non-affected PCT cells, what two proteins are affected by PTH?
1) PTH inhibits the NaPi transporter
2) PTH increases activity of 1-alpha-OHase
In chronic renal failure, what three consequences occur in the PCT as a result of a lack of response to PTH?
1) Hyperphosphataemia
2) Hypocalcaemia
3) Acidosis
What 3 pharmaceutical agents can be used for secondary hyperthyroidism?
1) Vitamin D supplementation
2) Calcimimetics
3) Phosphate binders
How does Vitamin D work in the context of secondary HPT?
Increases serum calcium and phosphate levels.
What are the issues with using Vitamin D as a treatment of secondary HPT?
Increases phosphate - already high because kidneys can’t get rid of it.
Slow onset.
Does nothing to reverse hyperplasia.
Give an example of a calcimimetic?
Cinacalcet
How often is cinacalcet taken?
1x daily