Osteoporosis Educational Series Lecture 2 of 3 Understanding

Osteoporosis Educational Series, Lecture 2 of 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 Objectives GOAL: 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 w Explain normal and abnormal state of bone metabolism w Define bone remodeling w Identify risk factors for bone loss w Calculate risk of facture

Pre Quiz Question 1 of 5 What percent of adult human bone is made of minerals? a) 20% b) 65% c) 75% d) 90%

Pre Quiz Question 2 of 5 Which of the following factors stimulate osteoblasts? (Choose one) a) b) c) d) Glucocorticoids and Estrogen Thyroxine and Androgen Estrogen and Growth Hormone Vitamin D and Thyroxine

Pre Quiz Question 3 of 5 Which one of the following statements best fits the pathological state of osteoporosis due to age related bone loss? a) b) c) d) Bone formation and resorption are in balance Both formation and resorption slows down at the same rate Both formation and resorption increases at the same rate Bone resorption is greater than bone formation

Pre Quiz Question 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) b) c) d) Diabetes Mellitus type II Hypothyroidism Diabetes Mellitus type I Osteogenesis Imperfecta in adults

Pre Quiz Question 5 of 5 In humans, trabecular bone volume is larger than cortical bone volume? a) True b) False

Why Do We Need Strong Bones: Function w Mechanical w w Weight bearing Protection for soft organs Attachment for muscles Mineral reservoir w w Calcium Phosphorus

Bone Structure Overall w Organic Matrix w w w Mineral Component w w 10% of adult bone Primarily protein collagen -provides flexibility 65% of adult bone Hydroxyapatite - insoluble salts of calcium (99%) & phosphorus (85%) Very little Mg, Na & HCO 3 Water w 25% of adult bone

Bone Structure Cellular w Osteoblasts w w Osteoclasts w w Critical to bone formation Reabsorb bone Osteocytes Osteoblasts Osteoclasts Exact role is still under investigation w Osteocytes

Bone Structure Types of bone Trabecular w w w 20% of skeletal mass Greater surface area than cortical Provides supporting strength to the ends of weight-bearing bones Cortical w w 80% of skeletal mass Solid outside shaft of long bones Forces on bone Compressive stress w From body weight pushing the bone down Tensile stresses w From muscles, pulling the bone apart

Trabecular and Cortical Bones Trabecular bone Cortical bone Mineral loss Tensile Comprehensive Healthy femur Femur with loss of mineral and microstructure

Physiology- Normal State Bone Marrow Progenitors Osteoblast Precursor Glucocorticoids Estrogen Androgens GH/IGF-1 Osteoblast Osteoclast Precursor _ _ + + *Find out if this is 1, 25 (OH)2 D Estrogen Calcitonin Thyroxine Vitamin A 1, 25 OHD PTH New Bone Formation Osteoclast Bone Resorption Osteocyte

Pathogenesis Of Osteoporosis - Bone Remodeling Osteoclast Precursor Mononuclear Osteoclast Cells Osteoblast Precursors Osteoblast LEGEND: LC = Lining Cells CL = Cement Line OS = Osteoid BRU = Bone Remodeling Unit Normal Bone Remodeling Sequence Resorption = Formation No change in bone mass

Basic Pathology High bone turnover state Unbalanced remodeling Osteoporosis Normal Bone Structure Osteoporotic Bone Structure

Unbalanced Remodeling & Osteoporosis Resorption > Formation Influencers: • Inadequate calcium or vitamin D • Menopause • Aging • Medications or diseases Net bone loss

Osteoporosis Risk Factors w w w w Increasing age Female gender Early menopause Low body weight Previous fracture Family history Low calcium intake w w w w Low vitamin D Alcohol Smoking Physical inactivity High caffeine intake Drug use- steroid White or Asian race

FRAX Calculator

FRAX Risk Factors w w w Age (40 -90), gender, height & weight Previous fracture Hip fracture in parents Current smoking Alcohol Glucocorticoids (oral) ≥ 3 months @ dose 5 mg daily or more w or equivalent doses of other glucocorticoids w w Rheumatoid arthritis Secondary osteoporosis w w w DM-I, OI in adults, Untreated hyper or hypothyroidism, Premature menopause (< 45 yrs), Chronic malnutrition or malabsorption & Chronic liver disease Bone mineral density (BMD)

Post Quiz Question 1 of 5 What percent of adult human bone is made of minerals? a) 20% b) 65% c) 75% d) 90%

Post Quiz Question 2 of 5 Which of the following factors stimulate osteoblasts? (Choose one) a) b) c) d) Glucocorticoids and Estrogen Thyroxine and Androgen Estrogen and Growth Hormone Vitamin D and Thyroxine

Post Quiz Question 3 of 5 Which one of the following statements best fits the pathological state of osteoporosis due to age related bone loss? a) b) c) d) Bone formation and resorption are in balance Both formation and resorption slows down at the same rate Both formation and resorption increases at the same rate Bone resorption is greater than bone formation

Post Quiz Question 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) b) c) d) Diabetes Mellitus type II Hypothyroidism Diabetes Mellitus type I Osteogenesis Imperfecta in adults

Post Quiz Question 5 of 5 In humans, trabecular bone volume is larger than cortical bone volume? a) True b) False

Thank You Questions?

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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