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A 34-year-old asthmatic male presents for a check-up. He has been taking low dose oral prednisone for over 10 years and although his asthma is well controlled, he is concerned about steroid-induced osteoporosis, because his grandfather, a type 1 diabetic, recently fell and broke his hip. Serum electrolytes, as well as a dual energy x-ray absorptiometry test (DEXA) of the spine and hip, are ordered. Which of the following additional tests would be recommended?
A. 1,25-dihydroxy vitamin D
B. C-terminal PTH
C. Intact PTH
D. Serum glucose
E. Serum protein electrophoresis
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The correct answer is D. This patient has a family history of diabetes. Steroid-induced diabetes mellitus is a frequent consequence of long-term corticosteroid therapy. It can be triggered by prednisone with or without a family history, but a predisposition may increase the risk. Symptoms such as polyuria and weight loss may be masked by the disease for which the patient is taking steroids.
Measurement of 1,25-dihydroxy vitamin D (choice A), the active vitamin D metabolite, would not be recommended. Corticosteroids can alter calcium balance mainly to due vitamin D deficiency secondary to impaired intestinal absorption of calcium, but 25-hydroxy vitamin D is a better marker for assessing nutrition.
PTH, an 84 amino acid polypeptide, can be cleaved into an active N-terminal fragment and an inactive C-terminal fragment. Measurement of C-terminal PTH (choice B) is not recommended. Although PTH is a regulator of calcium homeostasis, these fragment molecule measurements have not been found to correlate well with true PTH activity on bone.
Although PTH is a calcium regulator in the body, it is not considered a major contributor to corticosteroid-induced bone loss, so measurement of intact parathyroid hormone (choice C) is not the best choice. It is only significant if a person has underlying malabsorption such as inflammatory bowel disease.
Serum protein electrophoresis (choice E) is used mainly for the diagnosis of multiple myeloma in patients with pathologic fractures or a high clinical suspicion of myeloma.
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sorry about the delay!
i was having dinner! may consider it as early breakfast! its 2.15 am. time to sleep!
hope to take a day off tomorrow!
GL to you
catch u tomorrow
