Parathyroid and calcium Flashcards
What is the name of the hormone that the parathyroid hormone synthesises and from which cells in the parathyroid gland is this secreted from?
Parathyroid hormone
From the chief cells
What effect does the parathyroid have on calcium and phosphate levels and explain the effect of PT on the bones, kidneys and Gi tract
Increases calcium, decreases phosphate
Bones—>Increased resorption–>Increased calcium and increased phosphate
Gut- Increased Calcium absorptionby promoting formation of calcitriol in the kidneys
Kidneys: Less ca2+ excretion, increasded phosphate secretion
Name two types of cells in the parathyroid gland and what each do and describe them
chief cells: produce PTh: lots of nuclei
oxyphil cells: not sure: Lots of cytoplasm
Explain how calcitriol causes increased absoprtion of Ca2+
increases transcellular ptake
normally ca2+ taken up by paracellular
where is vitamin hydroxylated to its active form?
kidney and liver
How does decreasing levels of Ca2+ cause increased levels of PTH?
prolongs half life of RNA
Give symptoms of hypercalcaemia
tired, depressed, constipation, kidneys, bone and muscle aches
Two blood tests for hypercalcaemia?
Alkaline phosphatase: Enzyme on osteoplasts so increased osteoblast activity reflects increased alkaline phosphatase so increased bone turnover
Ca2+ levels
Causes of hypercalcaemia?
malignant osteolytic bone metastases
Multiple myeloma
Name 4 types of tumour that commonly metastasuse to bone?
breast, thyroid, renal, and lung
what is special about prostate tumours?
when metastasise to bone, they are osteoblastic metastases
6 common sites for bone metastases and why?
skull, proximal femur and humerus, ribs, vertebrae, pelvis
these produce a lot of blood cells so good blood supply
Define primary hyperparathyroidism
1 of the 4 glands has a adenoma that secretes PTH
Define secondary hyperparathyroidism
the 4 parathyroid glands have hyperplasia
Give two causes of secondary parathyroidism and what two things can cause this case?
vit D deficiency
chronic kidney disease due to failure to hydroxylate VitD
Describe the process of the effect of secondary hyperparathyroidism
Vit D deficiency–>less calcitriol–>less Ca2+ absorption from the gut
less Ca2+–>increased PTH secretion so increased bone resorption–>osteomalacia (if due to Vit D deficiency) or renal osteodystrophy
pateit comes in. Raised Phosphate, low calcium, raised alkaline phosphatase, raised PTH
secondary
Raised calcium, normal phosphate, raised alkaline phosphatase, low PTH
A malignancy causing hypercalcaemia
Raised calcium, low phosphate, raised alkaline phosphatase and raised PTH
primary hyperparathyroidism
When is hypocalcaemia seen?
thyroidectomy patients where parathyroid has been removed as well accidently
Explain the difference in symtpoms for hypo and hypercalcaemia
Hypo- Increased excitability of neurones so increased action potential firing –>tingling, epilepsy, tetany
Hyper- Decreased excitability—>lethargy, confusion, coma
How can hypocalcaemia kill
tetany of the laryngeal muscle
What is the difference between osteomaqlacia and osteoporosis
osteoporosis- Same ratio of bone to matrix, just less bone there
osteomalacia- Lower ratio of bone to matrix
Risk factors for osteoporosis? 6
post menopausal women low BMI Long term oral steroid use heavy drinking smoking prolonged inactivity
Treatment for hypercalcaemia?
rehydration
