Quantitative defect of bone characterised by reduced bone mineral density and increased porosity

Aetiology

• Loss of bone mineral density is physiological - starts at ~30 years
• Females tend to lose more bone mineral density after the menopause due to an increase in osteoclastic bone resorption with the loss of protective effects of oestrogen

Type I osteotoporosis

• Exacerbated loss of bone in the post‐menopausal period
• Early menopause may have an influence
• Familial and environmental factors (white Caucasians at particular risk)
• Further risk factors include smoking, alcohol abuse, lack of exercise and poor diet
• Colles fractures and vertebral insufficiency fractures tend to occur in this group

Type II osteoporosis

• Osteoporosis of old age with a greater decline in bone mineral density than expected
• Risk factors are similar with the added risks of chronic disease, inactivity and reduced sunlight exposure (Vitamin D)
• Femoral neck fractures and vertebral fractures predominate in this group

Secondary osteoporosis

Osteoporosis can also occur secondary to other conditions including:

• Drugs especially corticosteroid use and aromatase inhibitors (breast cancer)
• Alcohol abuse
• Malnutrition
• GI disorders - hepatic insufficiency, malabsorption, malnutrition, deficiency of vitamin C and D