Calcium and Parathyroid Hormone

Question 1

what does parathyroid hormones do?

Answer 1

• 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

Question 2

What is PTH response to decreased serum calcium?

Answer 2

• 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

Question 3

what does calcium homeostasis do?

Answer 3

negative feedback system
Return serum ionised calcium back to the set point of about 1.1 mmol/l

Question 4

what are the consequences of hypocalcaemia?

Answer 4

Parasthesia
* Muscle spasm
o Hands and feet
o Larynx
o Premature labour
* Seizures
* Basal ganglia calcification
* Cataracts
* ECG abnormalities o Long QT interval

Question 5

what are the common causes of hypoparathyroidism?

Answer 5

-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

Question 6

what can di George syndrome cause?

Answer 6

Hypoparathyroidism
Thymic aplasia
Immunodeficiency
Cardiac defects
Cleft palate
Abnormal facies

Question 7

what is di George syndrome?

Answer 7

Developmental abnormality of third and fourth branchial pouches

Question 8

what can autoimmune diseases cause

Answer 8

chronic mucocutaneous candidiasis, hypoparathyroidism, autoimmune adrenal insufficiency

Question 9

what infiltration can cause hypoparathyroidism?

Answer 9

Haemochromatosis o Wilson’s disease

Question 10

what can decreased PTH cause?

Answer 10

-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

Question 11

what is Pseudohypoparathyroidism?

Answer 11

Resistance to parathyroid hormone

Question 12

what is Pseudohypoparathyroidism caused by?

Answer 12

o Type 1 Albright hereditary osteodystrophy
– mutation with deficient Gα subunit
( caused by mutation of ga gene )

Question 13

what do people with Pseudohypoparathyroidism look like?

Answer 13

• Short stature
• Obesity
• Round facies
• Mild learning difficulties
• Subcutaneous ossification * Short fourth metacarpals * Other hormone resistance

Question 14

Pseudohypoparathyroidism

Answer 14

decrease serum calcium
high PTH
High bone resorption
high ca2+ absorption
high calcium reabsorption

Question 15

what are the common causes of hypercalcaemia?

Answer 15

• Tourniquet on for too long
• Sample old and haemolysed

Question 16

symptoms of Hypercalcaemia

Answer 16

Thirst, polyuria
* Nausea due to gut statis
* Constipation
* Confusion that can lead to a coma

Question 17

in chronic hypercalcaemia what are the chronic consequences?

Answer 17

• Renal stones
• ECG abnormalities * Short QT

Question 18

causes of hypercalcaemia

Answer 18

*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

Question 19

Hypercalcaemia of malignancy

Answer 19

increase in serum calcium2+
decrease in PTH
– decrease in bone resorption
decrease in ca2+ absorption
decrease in ca2+ reabsorption

Question 20

what are the consequences of primary Hyperparathyroidism

Answer 20

Bones
o Osteitis fibrosa cystica o Osteoporosis
* Kidney stones
* Psychic groans
o confusion
* Abdominal moans
o Constipation
o Acute pancreatitis

Question 21

what are 80% of Primary hyperparathyroidism due to?

Answer 21

• 80% due to single benign adenoma

Question 22

what are 15-20% of Primary hyperparathyroidism due to?

Answer 22

due to four gland hyperplasia
may be part of MEN 1 OR 11

Question 23

what are <0.5% of Primary hyperparathyroidism due to?

Answer 23

malignant

Question 24

describe primary hyperparathyroidism

Answer 24

increased PTH
increased bone resorption
- increased renal reabsorption of calcium
increased acclaim absorption
hypercalcaemia