Flashcards in Parathyroid: Science and Clinical Deck (50):
Main effect of parathyroid hormone
raise the blood calcium
What are the 3 main ways PTH raises blood calcium?
1. breaking down bone 2. increasing absorption of calcium from food 3. increasing the kidneys ability to hold onto calcium
7-dehydrocholesterol is converted by UV waves into ____________ or cholecalciferol
7-dehydrocholesterol is converted by UV waves into VITAMIN D3 or cholecalciferol
Where is cholecaliferol converted into calcidilol?
What is calcidilol?
Where is 25hydroxyVitaminD3 activated?
What is 25hydroxyVitamin D3 converted into in the kidney?
What is 1,25dihydroxyvitamin D3 also known as?
Calcitriol acts on the ____ of the kidney to increase calcium absorption
PCT - proximal convoluted tubule
Calcitriol actis on the gut to...
increase calcium and phosphate absorption
Calcitriol acts on the bone to...
increase resorption of calcium and phosphate
Calcitriol acts on the parathyroid gland...
in a negative feedback manner - inhibiting further PTH release
PTH acts on the ____ of the kidney to increase calcium reabsorption
DCT - distal convoluted tubule
PTH acts on the bone to...
activate the osteoblasts which subsequently activate the pre-osteoclasts
osteoclasts are a form of....
macrophage - they respond to macrophage colony stimulating factor
Action of calcitonin
released in response to raised plasma calcium and has opposite effects to PTH
Calcitonin is released from...
the parafollicular cells of the thyroid gland
the majority of cases of primary hyperparathyroidism are caused by...
a solitary adenoma
Symptoms which may be associated with primary hyperparathyroidism
weak, tired, thirsty, dehydrated, polyuria, renal stones, abdominal pain, pancreatitis, duodenal (less gastric) ulcers, fractures, osteoporosis or osteopaenia, increase BP
What genetic condition is primary hyperparathyroidism associated with?
What are the 3 Ps associated with MEN 1?
Parathyroid hyperplasia, Pancreatic endocrine tumours, Pituitary tumour
The MEN1 gene is a...
tumour suppressor gene
Investigations for primary hyperparathyroidism
raised Ca, raised or normal PTH, decreased phosphate, increased Alk Phos, 24 hr urinary Ca, DEXA, X-ray, CT
what should be avoided in primary hyperparathyroidism?
excess calcium and vitamin D intake, avoid thiazide diuretics
Surgery is always indicated with primary hyperparathyroidism - TRUE/FALSE
FALSE - surgery is only indicated if there is end-organ damage
Indications for surgery to treat hyperparathyroidism
bone disease, gastric ulcers, renal stones, osteoporosis, less than 50 years old, renal impairement (<60ml/min eGFR)
Drug that can be used in tertiary and carcinoma hyperparathyroidism
cinacalet - increases the PT to increased calcium thus reducing the production of PTH
Results from secondary hyperparathyroidism
decreased calcium and appropriately raised PTH
Causes of secondary hyperparathyroidism
decreased Vit D intake and chronic renal failure
Results of tertiary hyperparathyroidism
raised Ca and very raised PTH
cause of tertiary hyperparathyroidism
prolonged secondary hyperparathryoidsim causes glands to start acting autonomously - chronic renal failure
What is malignant hyperparathyroidism?
the release of PTH-related protein from some cancers
Cancers associated with malignant hyperparathyroidism?
squamous cell lung cancer, breast and renal cell carcinomas
results in malignant hyperparathyroidism
decreased PTH and raised Ca
Brief causes of hypoparathyroidism
congenital absence, destruction, autoimmune, hypomagnesia, idiopathic
Symptoms of hypocalcaemia
paraesthesia, muscle cramps, weakness, tetany, fatigue, bronchospasm, fits, Chovsteks sign, Trousseau sign, QT prolongation
Acute hypocalcaemia is an emergency which is treated with...
IV calcium gluconate, 10ml, 10% over 10 mins in 50ml dextrose
Long term management of hypocalcaemia
calcium supplement of 1-2g a day, Vit D tabs or depot injection
Why is magnesium so important for calcium?
calcium release from cells is highly dependent on magnesium
Causes of hypomagnesia
alcohol, drugs, GI illness, pancreatitis, malabsorption
Drugs which may cause hypomagnesia
thiazides and PPIs
a genetic defect in the GNAS1 gene
Test results in pseudohypoparathyroidism
low Ca, high PTH - cells are PTH resistant
what is pseudopseudohypoparathryoidism?
all of pseudohypoparathyroidism but with normal calcium
Rickets and Osteomalacia are caused by...
vitamin D deficiency
potential causes of vitamin D deficiency
gastric surgery, coeliac disease, liver disease, pancreatic failure, chronic renal failure, lack of sunlight, drugs i.e. anti-convulsants
Clinical signs of vitamin D deficiency
low calcium, muscle wasting (proximally), dental defects (caries and enamel), bone tenderness with deformity, fractures or pseudofractures
Blood results with osteomalacia
low Ca, low PO4, high Alk Phos, low Vit D, high PTH
malignancy associated with long term vitamin D deficiency