MCAT Biology Question 75: Answer and Explanation
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Question: 75
15. A genotypically female infant is born with ambiguous genitalia. Soon after birth, she suffers from hyponatremia, or low blood concentrations of sodium. Which endocrine organ is most likely to be affected?
- A. Hypothalamus
- B. Pituitary
- C. Kidneys
- D. Adrenal cortex
Correct Answer: D
Explanation:
The question stem states that an infant who is genotypically female is born with ambiguous genitalia, meaning that the genitalia do not appear to be specifically female or specifically male. In a genotypic female, this indicates that she was exposed to androgens during the fetal period. In addition, she is also losing sodium, causing hyponatremia. This indicates that she has two defects. First, she has excess androgens. Second, she is lacking in aldosterone, a hormone required for proper reuptake of sodium in the kidneys. Both of these hormones are synthesized in the adrenal cortex, making choice (D) the correct answer. Note that neither of these hormones is regulated by the hypothalamic–pituitary–adrenal axis, eliminating choices (A) and (B).