Examination of the Gastroenterology Patient for Metabolic Bone Disease

The diseases discussed in this chapter are all associated with inappropriately low BMD resulting from a variety of distinct mechanisms. Given that the causes of bone loss are distinct, the examination of the patient with GI-related metabolic bone disease should be tailored to the particular situation. Figure 55-2 presents an algorithm that is useful in various scenarios. Diseases such as celiac disease commonly cause osteoporosis. Indeed, in studies of asymptomatic osteoporotic women, 10% demonstrate antitissue transglutaminase antibodies suggesting that celiac disease may be a contributing factor for osteoporosis in the general population (Nuti et al, 2001). Diseases such as UC and, to a lesser extent, CD result in decreased BMD because of cumulative corticosteroid use; therefore tests of BMD such as dual-energy x-ray absorptiometry (DXA) are more important following steroid exposure. In addition to DXA testing, other tests such as quantitative (usually calcaneal)

TABLE 55-3. Mechanisms of Metabolic Bone Disease in Gastrointestinal and Hepatic Diseases

Mechanism Disorder Bone Disease

TABLE 55-3. Mechanisms of Metabolic Bone Disease in Gastrointestinal and Hepatic Diseases

Mechanism Disorder Bone Disease

Calcium and/or vitamin D deficiency

Intestinal malabsorption, (many causes); liver disease

Osteoporosis; osteomalacia

(25-hydroxyvitamin D deficiency)

Inflammatory cytokines

Crohn's disease; celiac sprue

Osteoporosis

Drug-induced

Glucocorticoids

IBD; Autoimmune hepatitis; post-OLT

Osteoporosis

Cyclosporine/Tacrolimus

IBD; post-OLT

Osteoporosis

Hypogonadism

IBD; celiac sprue; cirrhosis; glucocorticoid treatment

Osteoporosis

Hepatic osteodystrophy

Cholestatic liver disease; cirrhosis

Osteoporosis

IBD = inflammatory bowel disease; OLT = orthotopic liver transplantation.

IBD = inflammatory bowel disease; OLT = orthotopic liver transplantation.

Table 55-4. Choosing Bisphosphonates and Other Antiresorptive Therapies

(1) First line bisphosponates:

Alendronate (Fosamax)—10 mg/d or 70 mg/once per week; long half-life of 10 years therefore avoid in women with child-bearing potential Risedronate (Actonel)—5 mg/d or 35 mg/once per week; half-life of 20 days

(2) If gastrointestinal intolerance or worsening BMD after 1 year, consider the following alternatives:

a. Nasal calcitonin (Miacalcin)—although less effective than bisphosphonates, nasal absorption eliminates concern for poor gastrointestinal absorption.

b. IV bisphosphonates:

Pamidronate—although indicated for malignant hypercalcemia is also effective for glucocorticoid-induced osteoporosis (Boutsen et al, 1997, 2001) ; may use 30 mg IV given over 4 h. Half-life is 28 days. Should be repeated every 3 months.

Zoledronic Acid (Zometa)—dose is 4 mg IV over 15 minutes; effective to increase BMD in postmenopausal women for 1 year (Reid et al, 2002) Teriparatide (rDNA origin) (Forteo)—black box warning regarding potential risk of osteosarcoma seen in rats; very expensive; given by daily sc injection so avoids gut absorption

(3) Special circumstances:

Testosterone deficiency in men is suggested by low sexual drive and low BMD. Replacement can be achieved with topical gel (Androgel) or transdermal patches (many).

BMD = bone mineral density; IV = intravenous; sc = subcutaneous.

ultrasound or quantitative computed tomography may be used to assess BMD.

In addition to BMD measurements, other serum and urinary markers are available for assessment of bone turnover. Normally bone formation and bone resorption are tightly linked. N-telopeptide cross-linked of type 1 collagen is released with bone resorption and excreted in the urine. In patients with IBD, measurement of urinary N-telopeptide cross-linked of type 1 collagen was the best predictor of spinal bone loss over a 2-year follow-up period compared with other markers including bone alkaline phosphatase, osteocalcin, PTH, and vitamin D levels (Schulte et al, 2000).

For diseases in which malabsorption of vitamins and calcium may play a significant role in pathogenesis of BMD, such as celiac sprue, a baseline test of BMD is justified. Additional tests may also be necessary in order to correct the contributing metabolic deficiencies. These are shown in Figure 55-1. An interpretation of bone-related test results for common GI conditions is found in Table 55-1.

Why Gluten Free

Why Gluten Free

What Is The Gluten Free Diet And What You Need To Know Before You Try It. You may have heard the term gluten free, and you may even have a general idea as to what it means to eat a gluten free diet. Most people believe this type of diet is a curse for those who simply cannot tolerate the protein known as gluten, as they will never be able to eat any food that contains wheat, rye, barley, malts, or triticale.

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