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
how should FRAX be adjusted for patients on glucocorticoids
if prednisone equivalent > 7.5mg daily, increase major osteoporotic fracture risk by 15% and hip fracture risk by 20%
cause of hypocalcemia in a pt just started on chemo for lymphoma/leukemia
hyperphosphatemia from tumor lysis
breastfeeding mother with severe osteoporosis
pregnancy/lactation-associated osteoporosis
1 or more fragility fractures within 6 months after delivery
2/3 have predisposing risk factors (fam hx, heparin use, prolonged bedrest, etc)
osteogenesis imperfecta pt needs to be screened for what
hearing loss
most common type of osteogenesis imperfecta
type 1
fractures in youth»_space; adulthood
tx: bisphosphonates
xray features of impending atypical femur fractures in pts on bisphosphonate therapy
plain films with THICKENED femoral cortices
“dreaded black line” on femur xray
what to do if impending sign of atypical femur fractures on xray
ortho referral
what to do with when mild hypercalcemia detected in pt on thiazide diuretic
stop thiazide, recheck calcium/PTH in 3 months
what happens to BMD after liver transplant?
significant decline within the first 6 months, then improvement
reasons for high bone turnover after liver transplant
glucocorticoids
2’ hyperparathyroidism possibly due to renal effects of antirejection meds
what happens to BMD prior to liver transplant
low bone turnover state
which type of fractures has raloxifene been shown to prevent?
vertebral fractures
No effect on hip or other nonvertebral fxs
side effects of raloxifene
VTE
black box warning on teriperatide
osteosarcoma
do not use in pt with hx of skeletal irradiation, Paget’s, or unexplained elevation of alk phos
pt with nontraumatic mid-shaft femur fracture not on bisphosphonates, what is the next step?
image the contralateral femur for evidence of cortical thickening, which could suggest atypical femur fracture (frequently are bilateral)
what to do if early cortical bone changes are noted on femur xrays, consistent with early atypical femur fractures?
prophylactic femoral rod placement
which oral DM meds are associated with bone loss?
rosiglitizone
canagliflozin (but NOT dapagliflozin or empagliflozin)
should patients with nephrotic syndrome-associated hypercholesterolemia be treated?
yes. statin, ezetimibe, PCSK9 inhibitor, apheresis
phenotype of pseudohypoparathyroidism 1a
short, round face, short 4th metacarpal, developmental delay
phenotype of pseuedohypoparathyroidism 1b
normal
phenotype of pseudohypoparathyroidism 1c
similar to 1a
phenotype of pseudopseudohypoparathyroidism
similar to 1a, but no biochemical abnormalities
how to differentiate between pseudohypoparathyroidism and vit D resistance?
elevated 1,25 vit D in PTH resistance
treatment for 1st kidney stone, normal calcium/PTH
2L of fluids per day
pt with hypermagnesemia, high-normal serum calcium, family hx of hypercalcemia, what test to order next
24 hour urine calcium to look for FHH
mechanism of hypermagnesemia in FHH
inactivating CASR mutation in kidney, which leads to increased tubular calcium and magnesium reabsorption
