Hormonal Control of Calcium and Phosphate

Question 1

What really defines the deposition or reabsorption of the bone?

Answer 1

• [Ca] x [PO4] > solubility product ▶️ bone deposition

- [Ca] x [PO4]

Question 2

What indices suggest osteoblastic activity?

Answer 2

⬆️ osteocalcin, ⬆️ alkaline phosphatase

Question 3

What factor is associated with hyperglycemia in malignancy?

Answer 3

PTHrP

*most: myeloma and breast cancer

Question 4

What molecule do you measure when suspect a vitamin D deficiency?

Answer 4

25 OH vitamin D serum levels

Question 5

Why renal failure can lead osteoporosis (renal osteodystrophy)?

Answer 5

• loss nephrons ▶️ ⬇️ excretion of PO4 ▶️ ⬆️ plasma PO4 ▶️ ⬇️ Ca ▶️ ⬆️ PTH ▶️ bone resorption
• ⬇️ 1-Alfa hydroxylation ▶️ inactive vitamin D ▶️ vit D deficiency ▶️ ⬇️ Ca ▶️ ⬆️ PTH ▶️ bone resorption

Question 6

Treatment for primary hyperparathyroidism (hypercalcemia)

Answer 6

• surgery remove if is adenoma or most tissue if hyperplasia
• high volume fluid replacement
• bisphosphonate

Question 7

Specific target tissues of the PTH

Answer 7

• distal tubule ▶️ ⬆️ Ca reabsorption
• proximal tubule ▶️ (-) PO4 reabsorption (promotes excretion)
• kidney (+) 1-alfa-hydroxylase ▶️ convert active vitamin D
• bone resorption ▶️ ⬆️ Ca and PO4 into blood

Question 8

What is the main feature of pseudohypoparathyroidism, and what differentiate from primary hypoparathyroidism?

Answer 8

⬆️ PTH

Question 9

What is the cause of hypocalcemic-induced secondary hyperparathyroidism and in addition hyperphosphatemia? Is it a primary or secondary disorder?

Answer 9

Chronic renal failure - most common cause of secondary hyperparathyroidism

*exception because calcium and phosphate change in opposite direction, a properly of primary disorder

Question 10

How does phosphate decreases in secondary hyperparathyroidism, for example by vitamin D deficiency? How do you diagnose it?

Answer 10

• ⬇️ Ca ▶️ ⬆️ PTH ▶️ (-) phosphate reabsorption by kidney ▶️ excretion PO4 ▶️ ⬇️ plasma PO4
• ⬇️ plasma 25 OH vitamin D

Question 11

Why could you use PO4 binders in chronic renal failure?

Answer 11

Avoid ⬆️⬆️ plasma PO4 ▶️ ⬇️ Ca ▶️ ⬆️ PTH ▶️ bone resorption

Question 12

What do the excess and deficiency of vitamin D have in common?

Answer 12

Bone resorption ▶️ loss bone mass

Question 13

Inhibitor of RANKL. Disease to treat.

Answer 13

Denosumab. Osteoporosis