Endocrine System MCAT Practice Question
A researcher observes that chronic stress increases cortisol levels, which subsequently inhibits thyroid hormone secretion and immune cell proliferation. When cortisol is removed, these parameters do not immediately normalize. Which of the following best explains the delayed recovery?
Answer choices
- ACortisol has permanently damaged thyroid follicles, preventing hormone synthesis recovery
- BSustained cortisol elevation suppresses CRH and ACTH through negative feedback, requiring time for hypothalamic-pituitary axis re-sensitizationCorrect answer
- CCortisol irreversibly binds to glucocorticoid receptors, blocking their recovery even after hormone withdrawal
- DImmune cells destroyed by cortisol require de novo synthesis from bone marrow precursors, a slow process
- EThyroid peroxidase is permanently inactivated by cortisol, preventing iodine incorporation into thyroid hormones
- FCortisol-induced epigenetic modifications to immune cell genes create a prolonged hyporesponsive state that persists independent of circulating hormone levels
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