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Chapter 42: Agents That Affect Bone Mineral Homeostasis
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Which of the following drugs is routinely added to calcium supplements and milk for the purpose of preventing rickets in children and osteomalacia in adults?
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The 2 forms of vitamin D—cholecalciferol and ergocalciferol— are commonly added to calcium supplements and dairy products. Calcitriol, the active 1,25-dihydroxyvitamin D3 metabolite, would prevent vitamin D deficiency and is available as an oral formulation. However, because it is not subject to the complex mechanisms that regulate endogenous production of active vitamin D metabolites, it is not suitable for widespread use. The answer is A.
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Which of the following drugs is most useful for the treatment of hypercalcemia in Paget’s disease?
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Paget’s disease is characterized by excessive bone resorption, poorly organized bone formation, and hypercalcemia. Bisphosphonates and calcitonin are first-line treatments. Pamidronate is a powerful bisphosphonate used parenterally to treat hypercalcemia. The answer is C.
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The active metabolites of vitamin D act through a nuclear receptor to produce which of the following effects?
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(A) Decrease the absorption of calcium from bone
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(B) Increase PTH formation
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(C) Increase renal production of erythropoietin
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(D) Increase the absorption of calcium from the gastrointestinal tract
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(E) Lower the serum phosphate concentration
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The active metabolites of vitamin D increase serum calcium and phosphate by promoting calcium and phosphate uptake from the gastrointestinal tract, increasing bone resorption, and decreasing renal excretion of both electrolytes. They inhibit, rather than stimulate, PTH formation. The answer is D.
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A 59-year-old female was referred to your clinic for evaluation of osteopenia. She was diagnosed with adult-onset cystic fibrosis (CF). She reported being treated with prednisone 2 times in the past for CF exacerbations. Since menopause at 52 years of age, she had been treated with raloxifene for osteoporosis prevention. She also was on daily calcium and vitamin D supplementation. Her bone mineral density test revealed a T score of –1.6 at the lumbar spine, –2.2 at the left femoral neck, and ...