A 49-year-old man arrives at the office complaining of "aching bones." He has had insidious-onset pain in his back, pelvis, and lower extremities for the past two months. The pain is dull and worsens after performing weight-bearing activities. The patient has no prior medical history and is not on any medications. He moved to the United States from Central Africa five years ago and works overnight shifts as a cab driver. The vital signs are within normal ranges. A physical examination reveals normal muscle strength in both the upper and lower extremities. The diagnosis is established through a thorough laboratory evaluation. Following a discussion about the most likely cause of his condition, the patient begins spending more time outside in the sun. Which of the following enzymatic steps will most likely be affected by this change in activity?

Question

A 49-year-old man arrives at the office complaining of "aching bones." He has had insidious-onset pain in his back, pelvis, and lower extremities for the past two months. The pain is dull and worsens after performing weight-bearing activities. The patient has no prior medical history and is not on any medications. He moved to the United States from Central Africa five years ago and works overnight shifts as a cab driver. The vital signs are within normal ranges. A physical examination reveals normal muscle strength in both the upper and lower extremities. The diagnosis is established through a thorough laboratory evaluation. Following a discussion about the most likely cause of his condition, the patient begins spending more time outside in the sun.   Which of the following enzymatic steps will most likely be affected by this change in activity?

Quizplus · Accepted Answer

Eductional Objective: Sunlight causes the skin to convert 7-dehydrocholesterol to cholecalciferol (vitamin D3). Following 25-hydroxylation in the liver and 1-hydroxylation in the kidneys, the active form, 1,25-dihydroxyvitamin D, is formed. Inadequate sunlight exposure can result in vitamin D deficiency.

A 49-Year-Old Man Arrives at the Office Complaining of "Aching