Vitamins & Minerals · NEET PG Preparation Biochemistry
An exclusive breastfed 6-month-old infant presents with craniotabs, delayed closure of the anterior fontanelle, and widening of the wrists. Laborator…
Practice question from Vitamins & Minerals (NEET PG Preparation Biochemistry), with the correct answer and a step-by-step solution.
medium · MCQ · Q-9CDB9F
An exclusive breastfed 6-month-old infant presents with craniotabs, delayed closure of the anterior fontanelle, and widening of the wrists. Laboratory findings reveal hypocalcemia, hypophosphatemia, and elevated alkaline phosphatase. Which of the following is the primary mechanism of action of the active form of the vitamin deficient in this patient?
- A.Inhibition of osteoclast activity via calcitonin release
- B.Genomic action binding to intracellular receptors to increase intestinal calcium-binding proteinCorrect answer
- C.Direct enzymatic phosphorylation of bone matrix proteins
- D.Enhancement of renal calcium excretion to prevent nephrocalcinosis
Solution
The infant has rickets due to Vitamin D deficiency. 1,25-dihydroxyvitamin D3 acts through intracellular vitamin D receptors (VDR) to alter gene transcription, notably increasing the synthesis of calbindin-D (calcium-binding protein) in the intestinal mucosa to enhance calcium absorption.
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