Calcium and Parathyroid Hormone Flashcards
(24 cards)
what does parathyroid hormones do?
- increase calcium reabsorption
- decrease phosphate reabsorption
- increase 1 alpha hydroxylation of 25-oh via d
- increases bone remodelling
-bone respiration>bone formation
-increases calcium absorption beacause of increased 1,25 (OH02 VIT D
What is PTH response to decreased serum calcium?
- decrease in serum calcium
- increase PTH
- increase in bone resorption or increase in ca2+ reabsorption
- increase in urine phosphate
- decrease in serum phosphate
-incerase in 1,25 (OH)2 vit D - increase in ca2+ absporption
what does calcium homeostasis do?
negative feedback system
Return serum ionised calcium back to the set point of about 1.1 mmol/l
what are the consequences of hypocalcaemia?
Parasthesia
* Muscle spasm
o Hands and feet
o Larynx
o Premature labour
* Seizures
* Basal ganglia calcification
* Cataracts
* ECG abnormalities o Long QT interval
what are the common causes of hypoparathyroidism?
-surgical- most common cause with neck surgery can damage parathyroid
-radiation
- many rare syndrome e.g di George syndrome
-genetic
-auto immune
-infiltration
- magnesium deficiency w
what can di George syndrome cause?
Hypoparathyroidism
Thymic aplasia
Immunodeficiency
Cardiac defects
Cleft palate
Abnormal facies
what is di George syndrome?
Developmental abnormality of third and fourth branchial pouches
what can autoimmune diseases cause
chronic mucocutaneous candidiasis, hypoparathyroidism, autoimmune adrenal insufficiency
what infiltration can cause hypoparathyroidism?
Haemochromatosis o Wilson’s disease
what can decreased PTH cause?
-decreased renal calcium reabsorption—> increased relative calcium excertion
- increased renal phosphate reabsorption —> increased serum phosphate
-decreased bone resorption
- decreased formation of 1,25(OH) 2D— decreased intestinal calcium
—-> all cause decreased serum calcium
what is Pseudohypoparathyroidism?
Resistance to parathyroid hormone
what is Pseudohypoparathyroidism caused by?
o Type 1 Albright hereditary osteodystrophy
– mutation with deficient Gα subunit
( caused by mutation of ga gene )
what do people with Pseudohypoparathyroidism look like?
- Short stature
- Obesity
- Round facies
- Mild learning difficulties
- Subcutaneous ossification * Short fourth metacarpals * Other hormone resistance
Pseudohypoparathyroidism
decrease serum calcium
high PTH
High bone resorption
high ca2+ absorption
high calcium reabsorption
what are the common causes of hypercalcaemia?
- Tourniquet on for too long
- Sample old and haemolysed
symptoms of Hypercalcaemia
Thirst, polyuria
* Nausea due to gut statis
* Constipation
* Confusion that can lead to a coma
in chronic hypercalcaemia what are the chronic consequences?
- Renal stones
- ECG abnormalities * Short QT
causes of hypercalcaemia
*Malignancy
*bone mets , myeloma ,PTHrP ,lymphoma
** Primary hyperparathyroidism – 90% of causes are these
* Thiazides
* Thyrotoxocosis
* Sarcoidosis
* Familial hypocalciuric / benign hypercalcaemia * Immobilisation
* Milk-alkali
* Adrenal insufficiency
* Phaeochromocytoma
Hypercalcaemia of malignancy
increase in serum calcium2+
decrease in PTH
– decrease in bone resorption
decrease in ca2+ absorption
decrease in ca2+ reabsorption
what are the consequences of primary Hyperparathyroidism
Bones
o Osteitis fibrosa cystica o Osteoporosis
* Kidney stones
* Psychic groans
o confusion
* Abdominal moans
o Constipation
o Acute pancreatitis
what are 80% of Primary hyperparathyroidism due to?
- 80% due to single benign adenoma
what are 15-20% of Primary hyperparathyroidism due to?
due to four gland hyperplasia
may be part of MEN 1 OR 11
what are <0.5% of Primary hyperparathyroidism due to?
malignant
describe primary hyperparathyroidism
increased PTH
increased bone resorption
- increased renal reabsorption of calcium
increased acclaim absorption
hypercalcaemia
