Calcium and Parathyroid Hormone Flashcards
What are the actions of PTH?
Ca2+ reabsorption
Bone resorption
Indirect Ca2+ absorption (increased 1,25 (OH)2 vit D
Is it hypocalcaemia if low serum albumin, low total serum calcium but not a low ionised calcium?
No
What is the equation for working out corrected calcium?
total serum calcium + 0.02 * (40 – serum albumin)
What are consequences of hypocalcaemia?
- Parasthesia
- Muscle spasm
- Hands and feet
- Larynx
- Premature labour
- Seizures
- Basal ganglia calcification
- Cataracts
- ECG abnormalities
- Long QT interval
What is Chvostek’s Sign?
- Tap over the facial nerve
- Look for spasm of facial muscles
What is Trousseau’s Sign?
- Inflate the blood pressure cuff to 20 mm Hg above systolic for 5 minutes
- Hand forms shape
What could cause hypocalcaemia?
Vit D deficiency
What will the levels of PTH be like in vit D deficiency (secondary hyperparathyroidism)?
High
What will the levels of calcium be like in vit D deficiency (secondary hyperparathyroidism)?
Low
What will the levels of phosphate be like in vit D deficiency (secondary hyperparathyroidism)?
Low
Is the action of PTH appropriate or inappropriate in vit D deficiency (secondary hyperparathyroidism)?
Appropriate
- In attempt to raise calcium
- Increased phosphate excretion in kidney
What can cause hypoparathyroidism?
- Surgery
- Radiation
- Syndromes
- Developmental abnormality of third and fourth branchial pouches
- Genetic
- Autoimmune
- Infiltration
- Magnesium deficiency
How can surgery cause hypoparathyroidism?
- neck surgery can cause parathyroid to be damage
- Commonest cause
Which is the most common syndrome to cause hypoparathyroidism?
Di George
What will the levels of PTH be like in hypoparathyroidism?
Low
What will the levels of calcium be like in hypoparathyroidism?
Low
What will the levels of phosphate be like in hypoparathyroidism?
High
Is the action of PTH appropriate or inappropriate in hypoparathyroidism?
Inappropriate
What is psuedohypoparathyroidism?
- Resistance to parathyroid hormone
- Receptors on organs don’t respond to PTH
- Inherited
- Type 1 Albright hereditary osteodystrophy
- caused by mutation with deficient Gα subunit
What are the signs of pseudohypoparathyroidism?
- Short stature
- Obesity
- Round facies
- Mild learning difficulties
- Subcutaneous ossification
- Short fourth metacarpals
- Other hormone resistance
What will the levels of PTH be like in pseudohypoparathyroidism (PTH resistance)?
High
What will the levels of calcium be like in pseudohypoparathyroidism (PTH resistance)?
Low
What will the levels of phosphate be like in pseudohypoparathyroidism (PTH resistance)?
High
Is the action of PTH appropriate or inappropriate in pseudohypoparathyroidism (PTH resistance)?
Appropriate
- PTH acting normally, receptors resistant
What may look like hypercalcaemia actually be instead?
- Tourniquet on for too long
- Sample old and haemolysed
What are symptoms of hypercalcaemia?
- Thirst, polyuria
- Excess Ca
- Nausea
- Gut is a muscle, gut stasis
- Constipation
- Confusion → coma
What could chronic hypercalcaemia lead to?
- Renal stones
- ECG abnormalities
- Short QT
What is 90% of hypercalcaemia caused by?
- Malignancy
- bone mets, myeloma, some
tumours produce PTHrP,
lymphoma - PTHrP acts like PTH
- Lymphomas can activate
vitamin D
- bone mets, myeloma, some
- Primary hyperparathyroidism
What is 10% of hypercalcaemia caused by?
- Thiazides
- Thyrotoxocosis
- Sarcoidosis
- Familial hypocalciuric / benign hypercalcaemia
- Immobilisation
- Bone resorption
- Milk-alkali
- Usually in people with renal impairment
- Adrenal insufficiency
- Phaeochromocytoma
What will the levels of PTH be like in hypercalcaemia of malignancy?
Low
What will the levels of calcium be like in hypercalcaemia of malignancy?
High
What will the levels of phosphate be like in hypercalcaemia of malignancy?
Depends
Is the action of PTH appropriate or inappropriate in hypercalcaemia of malignancy?
Appropriate
What are consequences of Primary Hyperparathyroidism?
- Bones
- Osteitis fibrosa cystica
- Osteoporosis
- Kidney stones
- Psychic groans
- confusion
- Abdominal moans
- Constipation
- Acute pancreatitis
What is 80% of Primary Hyperparathyroidism due to?
single benign adenoma
- can be treated by minimally invasive parathydroidectomy
What is 15-20% of Primary Hyperparathyroidism due to?
- four gland hyperplasia
- All 4 glands overgrowing
- may be part of MEN I or II
What is <0.5% of Primary Hyperparathyroidism due to?
malignant
What will the levels of PTH be like in Primary hyperparathyroidism?
High
What will the levels of calcium be like in Primary hyperparathyroidism?
High
What will the levels of phosphate be like in Primary hyperparathyroidism?
Low
Is the action of PTH appropriate or inappropriate in Primary hyperparathyroidism?
Inappropriate