A 15-year-old girl asks why her linear growth is stopping despite continued nutrition and activity. The final event that leads to fusion of the epiphyseal plates in both sexes is best explained by:
- A Declining growth hormone secretion exhausting chondrocyte proliferation
- B Estrogen-mediated acceleration of chondrocyte maturation and plate ossification ✓
- C Testosterone acting directly on the resting zone of both sexes
- D Depletion of calcium stores causing mineralisation of the resting cartilage
Correct answer: B. Estrogen-mediated acceleration of chondrocyte maturation and plate ossification
Explanation
Estradiol is the final common mediator of epiphyseal fusion in both sexes; in males, testosterone acts largely after local aromatisation to estradiol. Estrogen accelerates chondrocyte hypertrophy, senescence and eventual replacement of the plate by bone. Growth hormone levels do not fall to zero at puberty and calcium depletion does not cause orderly plate fusion, which eliminates the distractors.
Reference: Ganong's Review of Medical Physiology, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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