A 41-year-old man presents to the physician for a routine health maintenance examination. He has been smoking one pack of cigarettes and drinking 4 beers daily for approximately 20 years. He works in construction and eats fish several days a week. His serum studies are as follows:
TSH: 2.1 (NR 0.5-5.0)
PTH: 60 pg/mL (NR 14-65)
25-OH-vitamin D3: Low
1,25-(OH)2-vitamin D3: Low
Which of the following is the most likely explanation for the findings in this patient?
Decreased cholecalciferol production
Decreased hepatic hydroxylation
Decreased mineralization of osteoid
Decreased proximal convoluted tubule hydroxylation
Decreased 7-dehydrocholesterol production
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Cut-to-the-chase Answer (1:01):
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HY USMLE Answer (4:02):
