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MCAT Question A Day - 6/21/14 - Answer!

patient develops an abdominal tumor resulting in the secretion of large quantities of aldosterone into the bloodstream. Which of the following will most likely occur?

A.  Levels of renin secreted by the kidney will increase.
B.  Levels of oxytocin secreted by the pituitary will increase.
C.  Levels of aldosterone secreted by the adrenal cortex will decrease.
D.  Levels of aldosterone secreted by the tumor will decrease.

C is correct. This is a negative feedback question. If another source of aldosterone exists in the body besides the adrenal cortex, negative feedback (through the renin-angiotensin system and increased blood pressure) would suppress the level of aldosterone secreted by the adrenal cortex. A is out because the levels of renin in the blood would decrease, not increase; aldosterone release would increase blood pressure, and renin is released in response to low blood pressure. OxytOCin plays no role in blood pressure (vasopressin does) and would not be affected by this tumor. Now, to choose between C and D: we know that aldosterone from the adrenal cortewould respond to negative feedback, but we aren't sure whether the tumor would. At this point, we know enough to go with C. If we're sure C is a correct response, that must mean D is an incorrect response, and we can eliminate it. In fact, this is a good choice because normally, hormone-secreting tumors will not respond to negative feedback.