Parathyroid gland Flashcards
How does the skeleton help to buffer serum calcium levels?
Through the release and uptake of calcium phosphate
What are the three functions of parathyroid hormone?
1) Stimulate bone resorption 2) Stimulates calcium reabsorption and phosphate excretion in the kidneys 3) Stimulates hydroxylation of VitD3 to its active form calcitrol
What are the two effects of calcitrol?
Increased absorption of Ca2+ at the kidneys and GI and increased bone resorption
PTH has a serum binding protein. True or false?
False
PTH is continuously synthesised but where is it stored?
PTH is not stored
Which cells is PTH secreted from?
Chief cells in the parathyroid gland
Where is the PTH-CA2+ receptor found?
On chief cells and in the kidney tubules
During high Ca2+, PTH degradation is …….
Stimulated
High serum phosphate, ….. PTH secretion
Stimulates
High serum magnesium, ….. PTH secretion
Inhibits
What are the target organs of PTH? (2)
Bone and kidney
Osteoclasts are stimulated by PTH. What is the role of osteoclasts?
They break down bone
Ca2+ is taken up in the small intestine. In which parts of the small intestine?
The duodenum and the jejenum
To activate vitamin D, how many hydroxylation reactions are required?
Two
What enzyme catalyses the formation of calcitrol from VitD3?
1a-hydroxylase
Where in the body is calcitrol formed?
The kidney proximal convoluted tubules
Hypocalcaemia leads to ……-……….. of the neuromuscular junction.
Hyper-excitability
What is the possible consequences of chronic hypercalcaemia?
Renal calculi, kidney damage, constipation, dehydration, tiredness and depression
What is the usual cause of primary hyperparathyroidism?
Parathyroid adenoma
PTH related peptide secreted from various tumours can lead to……
Over secretion of PTH
Hypocalcaemia can cause conditions such as rickets and osteomalacia. How?
Serum calcium concentrations is maintained at the expense of bone so bone density decreases
Does vitamin D stimulate or inhibit the uptake of phosphate in the gut?
Stimulate
Why does parathyroid hormones stimulate the calcium uptake but not phosphate?
It makes the formation of calcium-phosphate stones less likely
If serum calcium increases, which hormone is released and from where?
Calcitonin is release from the parafollicullar cells of the thyroid gland
Cell signalling is a function of Ca2+ in the body. True or false?
True
Parathyroid hormone is an amine hormone. True or false?
False. It is a peptide hormone.
Does calcitonin effect the GI tract?
No
How does the parathyroid gland sense plasma concentration?
The calcium receptors on the parathyroid gland are G-protein coupled receptors.
