Calcium and bones

Question 1

What do bisphosphonates do?

Answer 1

Inhibit osteoclastic activity, stabilize destructive boney tumors, reduce risk of pathological fracture and malignant hypercalcemia

(Zoledronic acid, pamidronate)

Question 2

Cause of hypocalcemia after thyroidectomy?

Answer 2

Hypoparathyroidism 2/2 removal of parathyroid glands due to parathyroid hyperplasia

Question 3

Electrolyte imbalance causing QT prolongation

Answer 3

HYPOcalcemia (less calcium -> slower repolarization)

Question 4

Electrolyte imbalance causing involuntary contractions (tetany) involving lips, face and extremities, and maybe seizures

Answer 4

Severe hypocalcemia

Question 5

Effect of PTH vs Vit D on Ca and Phos?

Answer 5

BOTH increase renal and GI absorption of Ca

PTH: Moar calcium in serum!
-> decrease Phos (bc CaPhos precipitates out!) thus reduces bone mass!!

VIT D MAKES STRONG BONES!
-> Increase Phos (to make CaPhos = stuff of bones!)

Question 6

Fractures in multiple stages of healing
Blue sclera
Short stature

What to do next?

Answer 6

Osteogenesis imperfecta

-> Type I collagen assay

Question 7

Symptoms of osteomalacia (vs. osteoporosis?)

Answer 7

Osteomalacia is mostly caused by vitamin D deficiency
Sx: Bone pain and muscle weakness
X-ray: pseudofractures (Looser zones), decreased bone density with thinning of cortex
(Less mineralization for the same amount of collagen vs. osteoporosis which has less of everything proportionally?)

Question 8

Lab values in Pagets

Answer 8

Elevated Alk-P. But NORMAL GGT! (This points to bone pathology instead of liver pathology)

Elevated PINP, urine hydroxyproline (bone turnover markers)
Calcium and Phos are usually normal!!!

Question 9

Osteolytic or mixed lytic/sclerotic lesions on X-ray

Mosaic “lamellar” bone pattern

Answer 9

Pagets

Question 10

Bone pain, decreased Ca, decreased PO4, secondary hyperparahyperthyroidism

Answer 10

Osteomalacia

Mineralizaitaon defect often due to severe vitamin D deficiency

Question 11

Diagnosis of osteoporosis

Answer 11

2.5 SDs below young, normal person on DEXA scan

1-2.5 SD = osteopenia

Question 12

Calcium, phos, PTH in osteoporosis?

Answer 12

Normal

Question 13

Bone pain +/- fractures, headaches, hearing loss

Answer 13

Pagets

Increased remodeling of bone -> both excessive resorption as well as formation of bone.

Question 14

Complications of Pagets

Answer 14

Pathological fractures
High-output heart failure (2/2 AV connections???)
Osteosarcoma (in up to 1%)

Question 15

High PTH, but low Ca and high Phos.

Answer 15

Pseudohyperparathyroidism (resistance to PTH)

Associated with Albright hereditary osteodystrophy (may have shortened 4th metatarsal or metacarpal bones)

Question 16

High calcium, but normal PTH.
Low urinary calcium.
Treatment?

Answer 16

Familial hypocalciuric hypercalcemia

Mutations in a calcium-sensing receptor present in parathyroid and kidney -> elevated serum Ca.