A woman with low serum cortisol due to partial adrenal dysfunction is treated with high doses of a synthetic cortisol analogue. According to Figure 2, treatment with a cortisol analogue will most likely cause this patient's serum level of endogenous cortisol to:


A.increase only.[4%]

B.decrease only.[51%]

C.remain the same.[4%]

D.increase at first, but then decrease over time.[39%]

The answer is B. I understand the whole negative feedback and how it would decrease but wouldn't it increase first and then decrease (D)??

I think the key here is "endogenous cortisol." Her overall cortisol levels will initially rise, but the endogenous "natural" cortisol will stay the same, and the body (which has to maintain homeostasis and regulate cortisol) will most likely breakdown/remove the "natural" cortisol faster than the synthetic.