Calcium/parathyroid Flashcards
which pseudohypoparathyroidism subclass has normal phenotype
PHP 1b
most common pseudohypoparathyroidism subclass
PHP 1a
gene associated with pseudohypoparathyroidism 1a
GNAS
phenotype of AHO but normal calcium/PTH
pseudopseudohypoparathyroidism
difference between osteomalacia and rickets
osteomalacia - disorder of mature (adult) bone
rickets - disorder of growing bone
defect in osteomalacia/rickets
mineralization of newly formed osteoid (bone protein matrix) is inadequate or delayed
most common cause of osteomalacia/rickets
vit D deficiency
enzyme that converts 25-OH vit D to 1,25-OH vit D
1 alpha hydroxylase
1,25-OH vit D acts on which tissues
intestine
kidney
parathyroid
bone
3 categories of osteomalacia/rickets
1) low calcium intake or vit D metabolism
2) disorders of phosphorus metabolism
3) small group of disorders with normal vit D/mineral metabolism
disorders of osteomalacia/rickets with normal vit D/phosphorus metabolism
hypophosphatasia
osteogenesis imperfecta
fibrogenesis imperfecta ossium
drugs (fluoride, aluminum, etidronate)
causes of phosphate deficiency/renal wasting
decreased phos intake
excessive aluminum hydroxide intake (phos binder)
x-linked hypophosphatemic rickets
autosomal dominant hypophosphatemic rickets
tumor-induced hypophosphatemia
renal tubular defects
2 genetic disorders that interfere with vitamin D synthesis or action
VDDR 1 - complete absence of renal 1-alpha hydroxylase activity
VDDR 2 - end-organ resistance to 1,25-OH vit D
phosphorus metabolism is regulated by which 3 factors
1,25-OH vit D
PTH
FGF-23
mechanism of XLH (x-linked hypophosphatemia)
inherited loss-of-function mutations in the PHEX gene, which leads to overexpression of FGF-23
FRAX score assumes glucocorticoid dose in what range
2.5-7.5mg prednisone daily