NEWSLETTER
Update on Osteoporosis
Dr. Asma Ahmed, Fellow, Diabetes, Endocrinology and metabolism, AKUH
Introduction
Osteoporosis is the most common bone disease affecting both men and women. With rapid aging of Asian population it happens to be one of the most prevailing health problems. It is expected that more than about 50% of all osteoporotic hip fractures will occur in Asia by the year 2050. Fractures caused by osteoporosis are associated with substantial morbidity and mortality and thus prevention and treatment of this disease is of paramount significance. It is diagnosed on the basis of low-impact or fragility fracture or low bone mineral density (BMD), which is best assessed by central dual-energy x-ray absorptiometry (DEXA). Both non-pharmacological & pharmacological treatment may be helpful in the prevention and treatment of osteoporosis. This article provides an overview of the definition, causes, diagnosis, clinical features, prevention & treatment of osteoporosis.
Definitions
In 1991, a consensus panel defined Osteoporosis as a chronic, progressive disease characterized by low bone mass, micro architectural bone deterioration, and decreased bone strength leading to increased bone fragility and a consequential increase in fracture risk. It is classified as primary or secondary. Primary is bone loss associated with aging process in both men and women. In primary the rate of activation of skeletal bone remodeling units is normal, but the filling of bone resorption pits is incomplete. Secondary Osteoporosis is bone loss caused by variety of chronic medical conditions, medications and nutritional deficiencies. Some common Endocrine causes of Osteoporosis are outlined in Table 1.
| Endocrine causes of Secondary Osteoporosis |
| Cushing Syndrome or corticosteroid therapy (eg 5mg/day for more than 3 months) |
| Hypogonadism |
| Hyperthyroidism or over-replacement of thyroxine |
Primary Hyperparathyroidism |
| Type 1 or 2 Diabetes |
Diagnosis and Evaluation:
Quantification of BMD at the lumbar spine and proximal femur by DEXA scan is a reliable and safe approach to assess the risk of fracture. This method is increasingly being used because of its excellent reproducibility (1-2%), low radiation exposure (less than 3 mrem) and short scan time (5-10 mins). WHO guidelines provide recommendations for the diagnosis of Osteoporosis and Osteopenia (Table 2).
| WHO Definitions of Osteopenia and Osteoporosis (applied both for men and women) | |
| Normal | Hip BMD >= 1.0 SD below the young adult female reference (T score above -1.0) |
| Osteopenia | ip BMD between 1.0 and 2.5 SDs below the young adult female reference mean ( T score between -1.0 and -2.5) |
| Osteoporosis | Hip BMD >= 2.5 SDs below the young adult reference mean (T Score at or below -2.5) |
| Severe Osteoporosis or established | Hip BMD >= 2.5 SDs below the young adult female reference mean in the presence of one or more osteoporosis fragility fractures. |
The current practice is to perform DEXA scan of the lumbar vertebrae (L1-L4); the hip; including the femoral neck, Ward's triangle, the greater trochanter, and the total hip, Of the hip measures, the femoral neck and the total hip, in particular are the most useful in predicting fracture. Because of the great variation in measurement at the Ward's triangle, it is of little clinical importance.
Laboratory Assessment:
Biochemical markers of increased bone resorption (collagen cross-links in serum or urine) or increased bone formation (bone specific alkaline phosphatase and osteocalcin) are linked with an increased fracture risk. However, their use in routine clinical practice is not recommended.
The history and physical examination can provide evidence of factors that contribute to the etiology of Osteoporosis. Routine laboratory testing should include creatinine, calcium, phosphorus, alkaline phosphatase and liver function tests. Given the extensive prevalence of vitamin D deficiency, 25 (OH) vitamin D levels should also be obtained. In patients with no apparent pathophysiology identified, 24 hr urinary calcium and creatinine is recommended to identify idiopathic hypercalciuria.
Clinical Manifestations:
The development of Osteoporosis is insidious. Acute pain associated with fracture is most often the first symptom. Patients can misinterpret acute backache as a muscle or ligament strain rather an Osteoporosis related fracture. Chronic backache could be another manifestation of Osteoporosis.
Treatment:
Prevention and treatment of Osteoporosis consists of non-drug and drug or hormonal therapy.
Nonpharmacologic Therapy: There are three components to the nondrug therapy of osteoporosis; diet, weight bearing exercises and cessation of smoking.
Pharmacological Therapy: Antiresorptive agents' bisphosphonates are effective for both the treatment and prevention of Osteoporosis
| Alendronate (Fosamax) | 35 - 70mg / week |
| Risendronate (Actonel) | 35mg/week OR monthly (150mg once monthly or 75mg tablets on two consective days each month) has similar efficacy for increasing spine and hip BMD as daily administration of 75mg |
| Ibandronate (Boniva) (also in IV Form) | Newer Bisphosphonate that is approved for prevention and treatment. 150mg/month or 2.5mg/day |
| IV Zolendronic acid (Aclasta, Zometa) | 4-5mg infusion of 15-30 minutes |
How long to treat
There is presently no consensus on how long to continue on bisphosphonate therapy. However, for some women, stopping therapy after five years may be reasonable, as there appears to be a residual benefit on BMD and fractures for up to five years. But in women with high risk of fracture, bisphosphonates are recommended to be continued for 10 years.
Adverse Effects
Gastrointestinal side effects have been the primary concern for patients taking oral bisphosphonates. To avoid this complication, it should be taken alone on an empty stomach first thing in the morning with at least 240 ml (8 oz) of water while sitting or standing to minimize the risk of pill associated esophagitis. After administration, the patient should not have food, drink, medications, or supplements for at least one-half hour.
| Other treatment modalities | |
| Raloxifene (Selective estrogen receptor modulator) | Approved for both prevention and treatment at a dose of 60mg/day |
| Calcitonin (not a first choice) | FDA approved for the treatment at a dose of 100-200 IU / day |
| Teriparatide (Recombinant PTH) | First anabolic drug approved for the treatment of osteoporosis. 20mcg/day |
| Combination Therapy | Researved for patients with severe osteoporosis |
Conclusion:
Osteoporosis is significant emergent public health problem that is under recognized but chiefly preventable and treatable. Bone mineral density (BMD) should be obtained routinely in all women over the age of 65 years and in men and younger women or men who have had a fragility fracture.
| Recommended Calcium and Vitamin D regime for the prevention and treatment of Osteoporosis | |
| Organization | Dose |
| National Osteoporosis foundation and American Association of Clinical Endocrinologist | 1200mg Calcium daily - 400-800 IU /day Vitamin D |