Metabolic Bone dz Flashcards
Osteoporosis:
- MOA
- describe hormonal control of bone homeostasis
MOA:
-bone resorption (osteoclast activity) outpaces bone deposition (osteoblast activity)
Bone homeostasis:
-if there is a decrease in plasma calcium causes a release of PTH from the parathyroid which effects the kidney, bone, and GI to increase serum calcium.
Describe how PTH effects:
- kidney
- bone
- GI
Describe how Calcitonin effects:
- kidneys
- bone
- GI
Kidney: PTH causes increased Ca resorption in the renal tubules and kidneys convert vit D to its active form.
Bone: increased osteoclast activity, releases Ca and PO4.
GI: increased absorption of Ca and PO4
CALCITONIN:
Kidney: decreased calcium and PO4 absorption
Bones: decreases osteoclast activity and decreases release of calcium
GI: decreased calcium absorption.
Which hormones induce osteoclast activity?
Describe the effects of hyperthyroidism on calcium metabolism?
Describe how the thyroid inhibits osteoclast activity?
PTH, low calcitonin, GF, IL-6, low estrogen increases IL-6.
Hyperthyroidism:
-thyroid hormones stimulate osteoclast activity thereby increasing plasma calcium.
Thyroid gland inhibits osteoclast activity when plasma calcium is increased by releasing calcitonin.
Risk factors of Osteoporosis.
WHat is the mnemonic for remembering these risk factors?
- Age (greater than 50)
- Gender (female)
- White/Asian
- Diet (ETOH, Tobacco, low Ca intake)
- Inactivity
- Hormonal (low estrogen/ lowtestosterone)(amenorrhea, late menarche, early menopause, post menopausal state)
- Meds (heparin/warfarin, loop diuretics, chemo drugs, GLUCOCORTICOIDS)
- FHx
- Medical hx
OSTEOPOROSIS:
- lOw Ca intake
- Seizure meds
- Thin build
- Etoh
- hypOgonadism
- Previous fx
- thyrOid excess
- Race (white/asain)
- Other relatives with osteoporosis
- Steroids
- Inactivity
- Smoking
Prevention of osteoporosis?
Exercise (weight bearing and muscle strengthening)
Appropriate Vit D and Ca intake
Cessation of tobacco
Avoidance of excessive alcohol intake
Screening tests (measure height, DXA)
T/F, Dexa scan is the standard test for evaluation of bone mineral density?
What are the indications for Dexa scan?
What are the DEXA screening guidlines?
True.
Indications:
- anyone currently being treated or considering pharmacologic therapy for osteoporosis.
- screening for osteoporosis
Guidlines for Dexa:
-all women greater than 65YO and men older than 70YO regardless of risk factors
- postmenopausal women and men (50-70) w/ risk factors)
- adults w/ fragility fx
- adults who have a condition associated with low bone mass (rheumatoid arthritis)
- adults who take medications associated with bone loss (steroids)
What is a T-Score?
what is indicated if T score is less than -2.5? Less than -2.5 w/ fragility fx?
-1 to -2.5?
T-score is used in Dexa Scan.
T score less than -2.5 = osteoporosis
T-score less than -2.5 + fragility fx = severe osteoporosis.
-1 to -2.5 = osteopenia
(if -1 this means they are one standard deviation away from the rest of the population for that age)
Dexa Scan:
-when is a Z score used?
Z-score used in premenopausal women, men younger than 50YO, and children.
- African americans and native americans.
- *T-score used in caucasians
Which test is effective at PREDICTING femoral neck, hip, and spine fxs?
Quantitative calcaneal US.
*if they have abnormal results they need to be referred for DEXA Scan.
Osteoporosis WOrk up?
Osteoporosis non-pharm Tx?
Hx
PE
Lab: CBC. CMP, serum magnesium, TSH, 25-OH Vit D, PTH, Testosterone, 24Hr urine calcium
+/- Xray (in sx patients, in asymptomatic pts if vertebral fx suspec)
Dexa scan
Tx: Caclium 1200mg, Vit D 800IU, exercise.
Osteoporosis Tx:
- SE of calcium
- SE Vit D
SE Calcium: nephrolithiasis, constipation, dyspepsia
SE Vit d:
-hypercalcemia, hypercalciuria, kidney stones.
Indications for Pharmacologic tx of osteoporosis?
Indications:
-older than 50YO AND they have a hip or vertebral fx
OR
-T score less than or equal to -2.5.
-T score -1.0 to -2.5 in postmenopausal men/women age 50YO and older PLUS 10year hip fx probability of greater than 3% or a 10Y major osteoporosis fx probability of greater than 20%.
Pharmacologic Tx options for Osteoporosis
- Bisphosphonates**(DOC)
- Calcitonin
- Estrogen agonist/antagonist
- Hormone therapy
- Parathyroid hormone
- RANKL inhibitor (Denosumab)
- Tissue selective estrogen complex
Bisphosphonates:
- drugs
- route of admin
- MOA
- half life
- renal dosing?
- complications
- CI
Drugs & Route:
-Alendronate (Fosamax) & Risedronate (Actonel) are PO.
Zoledronic acid (Reclast) & Ibandronate (Boniva) are IV.
MOA: inhibit bone resorption by decreasing the number and function of osteoclasts.
Half life: 1hr in plasma, in bone may persist for a lifetime.
Renal dosing: GFR needs to be greater than 30-35ml/min
Complications:
-erosive esophagitis, (make sure they can remain upright and drink a big glass of water after they take a pill)
CI:
- barretts esophagus
- active upper GI Dz
- GFR less than 30-35ml/min
Bisphosphonates:
- admin directions
- duration of therapy?
Admin directions:
- take on an empty stomach, drink 8oz of water and remain sitting upright for 1hr.
- tx is daily, weekly or monthly for PO drugs.
Duration:
- at 5 years reassess the need, actually every time you see the pt you should reconsider if they need this therapy.
- after 10 years the medications have done what they are going to do. if your going to have them on it for over 10 years have a reason.