Review Question - QID 104347

An elderly woman with bone pain and history of low dairy intake combined with lack of sunlight exposure is likely suffering from osteomalacia. The next best test to confirm the diagnosis is 25-hydroxyvitamin D.

Vitamin D deficiency commonly presents as lower back pain, proximal muscle weakness, muscle aches, and bone pain elicited with pressure. To confirm the diagnosis, a 25-hydroxyvitamin D level should be obtained in patients with suspected vitamin D deficiency. Deficiency is defined as a serum 25-hydroxyvitamin D level of less than 20 ng per mL. Treatment of choice is repleting vitamin D stores with the goal in adults to decrease the risk of fractures and falls.

Bordelon et al. discuss recognition and management of vitamin D deficiency in adults. Risk factors include age over 65, dark skin, poor diet (no dairy), insufficient sunlight exposure, medications that alter vitamin D metabolism (e.g. anticonvulsants), and sedentary lifestyle. They also state that previous studies with vitamin D dosage of 700 to 800 IU per day reduced the relative risk of hip fracture by 26 percent and the relative risk of nonvertebral fracture by 23 percent when compared with calcium supplementation alone or placebo.

Moraes et al. report on the effect of vitamin D deficiency in critically ill patients. In their study, they report that vitamin D deficiency is an independent risk factor for increased mortality in this patient population. They show that mortality rates were higher among patients with vitamin D levels <12 ng/mL (32.3%) versus vitamin D levels >12 ng/mL (13.3%), with an adjusted relative risk of 2.2 (P<0.05).

Illustration A shows the conversion of vitamin D to its active form, 1,25-hydroxyvitamin D.

Incorrect Answers:
Answer 1 and 4: 7-Dehydrocholesterol in the skin gets converted to pre-vitamin D3 and is therefore not an accurate representation of the patient's vitamin D stores.
Answer 3: 1,25-Hydroxyvitamin D is the active form of vitamin D found in the human body. Its levels fluctuate with levels of parathyroid hormone and calcitonin therefore it is not the best representation of the patient's vitamin D stores.
Answer 5: Dietary vitamin D2 and D3 levels change on a daily basis and are therefore not best representation of the patient's vitamin D stores.