Parathyroid gland physiology and disease

Question 1

where is the majority of calcium found in the body, and what percentage?

Answer 1

99% found in bone

Question 2

what percentage of the body’s calcium is found in the extracellular space?

Answer 2

0.9%

Question 3

what is the normal range of values for free ionised calcium in the blood?

Answer 3

2.20 - 2.60

Question 4

of the 0.9% of calcium found in the extracellular space, how much of it is bound to proteins and other molecules?

Answer 4

about half

Question 5

how does pH affect the amount of free calcium in the blood?

Answer 5

lower pH - more H attach to albumin, displacing Ca2+ and raising free amount in blood
high pH - less H - more Ca2+ attach to albumin resulting in lower free Ca2+ levels

Question 6

which hormones control the calcium levels in the blood? where are they released from and what is their action?

Answer 6

parathyroid hormone (parathyroid gland) - increases Ca2+ levels
calcitonin (thyroid gland) - reduces Ca2+ levels

Question 7

through which actions does parathyroid hormone regulate calcium levels in the blood?

Answer 7

• it stimulates bone resorption by osteoclasts, resulting in release of Ca2+ and phosphate
• it stimulates Ca2+ reabsorption at the kidney’s distal tubule
• it stops reabsorption of phosphate at kidney’s proximal tubule
• it stimulates Vit D activation by kidneys to absorb more Ca2+ in GI tract

Question 8

list some of the main causes of hypocalcaemia

Answer 8

hypoparathyroidism (post surgery, radiation, autoimmune)
pseudohypoparathyroidism
vitamin D deficiency
renal disease
acute pancreatitis
low magnesium 
drugs (eg bisphosphonates)

Question 9

list some of the main causes of hypercalcaemia?

Answer 9

tumours: MEN, hyperparathyroidism, other malignancy
vitamin D excess
renal failure
familiar hypocalciuric hypercalcaemia

Question 10

list some phenotype characteristics of a patient with pseudohypoparathyroidism

Answer 10

AHO
obesity
short stature
short 3/4 fingers
low calcium with high PTH levels

Question 11

list some additional tests that should be done if calcium level abnormalities are found in the blood

Answer 11

PTH
magnesium
phosphate
vitamin D
glucose
LFT
U&E
creatinine

Question 12

list some signs of hypocalcaemia

Answer 12

tetany
muscle spasms
chvostek's sign
trousseau's sign
arrythmia
prolonged QT segment
papilloedema
seizures

Question 13

what is the management of mild hypocalcaemia?

Answer 13

calcium administration
vitamin D administration if deficient
magnesium administration if deficient
stop drugs lowering magnesium

Question 14

what is the management of acute, severe hypocalcaemia?

Answer 14

IV calcium gluconate

treat underlying cause

Question 15

list some signs of hypercalcaemia

Answer 15

polydipsia
polyuria
kidney stones
short QT interval
constipation
poor concentration
muscle weakness
kidney injury
dehydration
N&V
anorexia

Question 16

what is the general management of hypercalcaemia?

Answer 16

fluids to stop dehydration

IV bisphosphonates

Question 17

how is primary hyperparathyroidism normally treated (surgically and medically)?

Answer 17

surgical: resect parathyroid adenoma
medical: fluids, then calcium mimetics to lower PTH levels

Question 18

what are the two common causes hyperparathyroidism?

Answer 18

parathyroid adenoma

parathyroid hyperplasia

Question 19

what is MEN?

Answer 19

multiple endocrine neoplasia

Question 20

which organs are affected in MEN1?

Answer 20

Pancreas
Parathyroid
Pituitary

Question 21

which organs are affected in MEN2A?

Answer 21

Parathyroid
Adrenal medulla (Phaeochromocytoma)
Thyroid medulla (Medullary thyroid cancer)

Question 22

in the pituitary gland, which hormones are secreted by acidophils and which are produced by basophils?

Answer 22

acidophils - growth hormone and prolactin

basophils - ACTH, TSH, FSH, LH,