osteoporosis educational series, lecture 2of 3: understanding bone to understand osteoporosis:...
TRANSCRIPT
Osteoporosis Educational Series, Lecture 2of 3: Understanding Bone to Understand Osteoporosis: Pathogenesis and Risk Factors
Nahid Rianon, M.D., Dr.P.H.The University of Texas Health Science Center at Houston
Goal and ObjectivesGOAL: The goal of this presentation is to describe detail
mechanism of bone loss and risk of fractures
LEARNING OBJECTIVES:At the end of this presentation, attendees will be able to
Explain normal and abnormal state of bone metabolism Define bone remodeling Identify risk factors for bone loss Calculate risk of facture
What percent of adult human bone is made of minerals? a) 20% b) 65%c) 75%d) 90%
Pre QuizQuestion 1 of 5
Which of the following factors stimulate osteoblasts? (Choose one)
a) Glucocorticoids and Estrogenb) Thyroxine and Androgenc) Estrogen and Growth Hormone d) Vitamin D and Thyroxine
Pre QuizQuestion 2 of 5
Which one of the following statements best fits the pathological state of osteoporosis due to age related bone loss?
a) Bone formation and resorption are in balanceb) Both formation and resorption slows down at the same ratec) Both formation and resorption increases at the same rated) Bone resorption is greater than bone formation
Pre QuizQuestion 3 of 5
Which of the following diseases is not considered a risk for developing secondary osteoporosis (when remains untreated) for FRAX calculation tool?
a) Diabetes Mellitus type IIb) Hypothyroidismc) Diabetes Mellitus type Id) Osteogenesis Imperfecta in adults
Pre QuizQuestion 4 of 5
Pre QuizQuestion 5 of 5
In humans, trabecular bone volume is larger than cortical bone volume?
a) Trueb) False
Function
Mechanical Weight bearing Protection for soft organs Attachment for muscles
Mineral reservoir Calcium Phosphorus
Why Do We Need Strong Bones:
Overall
Organic Matrix 10% of adult bone Primarily protein collagen -provides flexibility
Mineral Component 65% of adult bone Hydroxyapatite - insoluble salts of calcium (99%) & phosphorus (85%) Very little Mg, Na & HCO3
Water 25% of adult bone
Bone Structure
Cellular
Osteoblasts Critical to bone formation
Osteoclasts Reabsorb bone
Osteocytes Exact role is still under investigation
Bone Structure
Osteoblasts
Osteoclasts
Osteocytes
Types of bone Forces on bone
Trabecular 20% of skeletal mass Greater surface area than cortical Provides supporting strength to
the ends of weight-bearing bones
Cortical 80% of skeletal mass Solid outside shaft of long bones
Compressive stress From body weight pushing the
bone down
Tensile stresses From muscles, pulling the bone
apart
Bone Structure
Trabecular and Cortical Bones
Trabecular bone Cortical bone
Femur with loss of mineral and microstructure
Healthy femur
Tensile
Comprehensive
Mineral loss
Physiology- Normal State
Bone Marrow Progenitors
Osteoblast Precursor Osteoclast Precursor
Glucocorticoids Estrogen Calcitonin
Estrogen AndrogensGH/IGF-1
Thyroxine Vitamin A
Osteoblast
New Bone Formation
Bone Resorption
Osteoclast
Osteocyte
1,25 OHDPTH
+
_ _
*Find out if this is 1,25 (OH)2D
+
Pathogenesis Of Osteoporosis - Bone Remodeling
Normal Bone Remodeling Sequence
Resorption = Formation No change in bone mass
LEGEND: LC = Lining Cells CL = Cement Line OS = Osteoid BRU = Bone Remodeling Unit
OsteoclastPrecursor
OsteoclastOsteoblastPrecursors Osteoblast
MononuclearCells
High bone turnover state
Unbalanced remodeling
Osteoporosis
Basic Pathology
Normal Bone Structure
OsteoporoticBone Structure
Resorption > Formation Net bone loss
Unbalanced Remodeling & Osteoporosis
Influencers:
• Inadequate calcium or vitamin D
• Menopause
• Aging
• Medications or diseases
Increasing age Female gender Early menopause Low body weight Previous fracture Family history Low calcium intake
Low vitamin D Alcohol Smoking Physical inactivity High caffeine intake Drug use- steroid White or Asian race
Osteoporosis Risk Factors
FRAX Calculator
Age (40-90), gender, height & weight
Previous fracture Hip fracture in parents Current smoking Alcohol Glucocorticoids (oral) ≥ 3
months @ dose 5mg daily or more
or equivalent doses of other glucocorticoids
Rheumatoid arthritis Secondary osteoporosis
DM-I, OI in adults, Untreated hyper or
hypothyroidism, Premature menopause (< 45
yrs), Chronic malnutrition or
malabsorption & Chronic liver disease
Bone mineral density (BMD)
FRAX Risk Factors
Post QuizQuestion 1 of 5
What percent of adult human bone is made of minerals? a) 20% b) 65%c) 75%d) 90%
Post QuizQuestion 2 of 5
Which of the following factors stimulate osteoblasts? (Choose one)
a) Glucocorticoids and Estrogenb) Thyroxine and Androgenc) Estrogen and Growth Hormone d) Vitamin D and Thyroxine
Post QuizQuestion 3 of 5
Which one of the following statements best fits the pathological state of osteoporosis due to age related bone loss?
a) Bone formation and resorption are in balanceb) Both formation and resorption slows down at the same ratec) Both formation and resorption increases at the same rated) Bone resorption is greater than bone formation
Post QuizQuestion 4 of 5
Which of the following diseases is not considered a risk for developing secondary osteoporosis (when remains untreated) for FRAX calculation tool?
a) Diabetes Mellitus type IIb) Hypothyroidismc) Diabetes Mellitus type Id) Osteogenesis Imperfecta in adults
In humans, trabecular bone volume is larger than cortical bone volume?
a) Trueb) False
Post QuizQuestion 5 of 5
Questions?
Thank You
Reference
• American Society for Bone and Mineral Research http:www.asbmr.org• WHO Fracture Risk Assessment Tool (FRAX)
http://www.sheffield.ac.uk/FRAX/tool.jsp
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