OSTEOPOROSIS

Osteoporosis: A condition characterized by an abnormally low bone density which results from the loss of both mineral and matrix from bone and is associated with an increased risk of fracture.

 

• Affects 24 million American a year.
• Correlated with 1.3 million fractures per year.

 

Pathogenesis:

Cortical bone-very dense bone that make up the exterior surface of the bone and is thickest at areas of stress.

 

• Approximately 25% is lost fro ages 50-80 years
• Peak bone mass 35 yes

Trabecular bone-loosely woven beams of bone that make up the interior of the bone and is located primarily at the bulbous ends of long bones.

• Vertebrae and ribs
• Peak bone mass in 25 years

Bone remodeling:

• Osteoclasts (bone cells)-cause the breakdown and resorption of bone.
• Osteoblasts (bone cells)-synthesize collagen, build bone and are responsible for bone maintenance.

 

 

Common Sites of Fracture:

• Vertebrae
• Pelvis
• Femur
• Radius
• Ulna
• Sacrum
• Wrist
• Humerus
• Ankle
• Tibia

 

Mechanisms of Bone Loss:

• Osteoclast mediated --rapid bone loss occurring immediately after menopause.
• Osteoblast mediated -- slow age-related bone loss.

Hormonal Factors Affecting Bone Metabolism:

• Estrogen

-- decreases bone resorption

-- promotes calcium retention (by increasing calcitrol and calcitonin)

• Parathyroid Hormone (PTH)

-- increases response to low serum calcium concentrations

-- increases bone resorption

-- increases calcitriol which increases calcium absorption

-- decreases calcium excretion

• Calcitonin

-- increases in response to high serum calcium concentrations

-- decreases bone resorption

-- increases calcium excretion

Types of Osteoporosis

1. Primary- general bone deficiency

	Type I	Type II
Other names	post-menopausal	senile geriatric
Risk	female > male	female = males
Bone loss	rapid	slow
Age (years)	50-70	70-90
Fracture site	vertebrae	hip

1. Secondary - caused by identifiable agents or disease

Risk Factors:

• Women-

-- smaller skeletons and 10-25% less bone mass than men

-- faster rate of bone loss than men

--women bone loss begins at approximately age 35 at 1% per year until menapause. 5 years after menapause, bone loss increases to 2-4% per year; then the rate returns to the premenopausal rate of 1% loss per year.

--men do not lose bone until the mid-forties with a rate loss of 0.4-0.5% per year.

• Menopause/Premature Menopause - estrogen decreases, calcium mobilizes
• Sedentary lifestyle, immobilization, physical inactivity
• Small body build - obese produce more estrogen which protects against bone loss.
• Race - white greatest
• Age - increases
• Family history
• Low calcium intake (RDA=800-1000 mg/day premen; 1200-1500 mg/day postmen)
• Vitamin D deficiency
• Excessive coffee intake
• High protein intake

Screening methods for osteoporosis

• Urine tests

fasting calcium/creatinine, fasting hydroxyproline/creatine

 

• Blood tests

Calcium/phosphorous: 1,25(OH)2Vitamin D3

Progesterone; Estrogens (estradiol, estrone)

Serum Gla-protein

 

• Photon Absorptiometry

single, dual

 

• Computed tomography

Female Athlete Triad

(Disordered Eating, Amenorrhea, Osteoporosis)

Oligomenorrhea - irregular menstrual periods (menstrual periods once every 39-90 days)

Amenorrhea - complete cessation of menstrual periods for 90 days or more which may be associated with abnormally low estrogen levels.

Factors that Increase Bone Density:

• Gravity
• Anatomical site of maximal stress
• Repetitive movements - aerobic training entails continuous repetitive movement
• Estrogen replacement therapy

Exercise-Induced Amenorrhea - Risk for Osteoporosis

• Incidence is 6-18%; up to 50% in runners (>80 miles/week)
• Less than 17% body fat; 17% body fat is generally required for menstruation
• Establishment of menarche and parity (previously had children)

--Age at which the athletic training begins - increase in irregularities if training begins prior to regular menstrual function.

--Nulliparous vs. parous women - women who have had no children have twice the risk of developing amenorrhea.

--History of menstrual irregularity

 

• Exercise intensity and duration increases incidence
• Stress - emotional, physical
• Nutrition - quest to be thin, improper eating habits, low calorie intake

Hormone Levels of Amenorrheic Athletes:

• Estrogen - low levels are responsible for cessation of menses
• Progesterone - low
• Luteininzing hormone - low levels stimulate ovulation

 

Managing Amenorrhoeic Athletes

Gynaecological Assessment

Nutritional Assessment

Reduction in Training Intensity

Increase in Calorie Intake

Consider Estrogen Replacement Therapy (Birth Control Pills)

Effects of Exercise-Induced Amenorrhea on Bone:

• Lower trabecular bone density
• Lower peak bone mass - especially in athletes that start training at a young age.
• Low estrogen levels cause bone mass to decrease
• Low vitamin intake causes a change in bone metabolism.

Treatment of Osteoporosis in Female Athletes:

• Non-drug therapy - decrease training to a point where regular menstruation resumes and/or increase body fat to 22%.
• Birth control pills -estrogen supplementation helps sustain athletes bone mass and estrogen inhibits bone resorption.
• Calcium and/or vatamin D supplementation - if the athlete is not eating right.

Prevention of Osteoporosis:

• Adequate intake of calcium throughout life
• Calcium supplementation
• Estrogen replacement - treat continuously for 10-15 years after menapause
• Oral contraceptives
• Progestogens

medroxyprogesterone (Provera)

norethindrone (Norlutin)

norethindrone acetate (Norlutate)

• Vitamin D Supplementation

--sunlight

--Rocatrol - active form of vitamin D

• Calcitonin - men and women who cannot take estrogens.
• Anabolic Steroids - equal to estrogens but not FDA approved.

Treatment of Post-menapausal Osteoporosis:

• Aldendronate Sodium (Fosamax)

-- Works in the treatment of osteoporosis and other bone conditions by inhibiting bone resorption.

 

-- Mechanism of action involves the alteration of osteoblast and osteoclast activity or reductions in the number of osteoclasts at the site.

 

Treatment of Osteoporosis:

• Fluoride - only known agent to stimulate trabecular bone formation and not all patients respond.
• Exercise - weight bearing, only known natural means of treatment

-- piezoelectric effect - electric current induced by bending and mechanical stress

-- stimulate osteoblasts

-- increases the serum levels of vitamin D

-- increases calcitonin levels

-- slows the rate of bone loss

-- stimulates the secretion of growth hormone

-- maintains a positive calcium balance.

 

• Glucosamine (Chondroitin) - treatment of arthritis in combination with vitamin C.

-- currently very popular in older individuals

-- popular for dogs diagnosed with hip dysplasia.

 

Patient Counseling:

• Exercise
• Discuss adequate calcium and vitamin D intake
• Caution patients on the use of drugs that may cause dizziness and disorientation (alcohol, antidepressants, benzodiazepines, antihypertensives, etc.)
• Caution patients about objects which may cause them to fall

-- small pets

-- cords and wires on the floor

-- improper use of walker or cane

-- low seating (toilets and chairs)

-- poorly fitting footwear

-- poor lighting

-- slippery walking surfaces

-- throw rugs

-- unstable furniture