calcium metabolism 2

Question 1

causes of hypercalcaemia

Answer 1

• primary hyperparathyroidism
• cancer-associated
• vitamin D toxicity
• familial benign hypercalcaemia

> 95% of cases are due to one of these

Question 2

hypercalcaemia and cancer

Answer 2

solid tumours secreting PTHrP

multiple skeletal metastases

bone marrow malignancy - secretion of cytokines stimulating bone resorption

Question 3

alkaline phosphatase

Answer 3

comes from liver and bone

if elevated can mean osteomalacia (would have low Ca2+ and high PTH)

Question 4

osteomalacia

Answer 4

failure of bone to mineralise

• low dietary Ca2+
• malabsorption
• increased renal phosphate loss
• vitamin D deficiency
• osteoblast dysfunction

in childhood = rickets

Question 5

what does 1,25 dihydroxyvitamin D do?

Answer 5

increase fractional calcium and phosphate absorption

without it can result in poor diet and GI disease

Question 6

who is most at risk of vitamin D deficiency

Answer 6

house-bound/institutionalised elderly that get little sunlight exposure

individuals with pigmented skin as pigments screen out UVb component

individual who protect their skin for medical or cultural reasons

impaired 1 alpha hydroxylase

Question 7

phenotype of PTH resistance

Answer 7

(low Ca2+, high PTH)

short stature
short 4th & 5th metacarpal and metatarsal

Question 8

autosomal dominant hypocalcaemia with hypocalciuria

ADHH

Answer 8

• decreased PTH
• decreased sCa2+
• increased uCa2+

autosomal dominant inheritance
hypocalcaemia

Question 9

ADHH

Answer 9

• no Tx if asymptomatic

- small doses vitamin D if recurrent symptoms