Review Question - QID 215010

A 5-year-old boy presents to the primary care clinic for 2 weeks of weakness and muscle cramps. His parents have noticed that he is much less active than other children and he prefers napping to physical activities. Other children tend to avoid him on the playground, especially on warmer days. He has a history of eczema for which he regularly uses a topical hydrocortisone cream. He is otherwise growing normally and has met all developmental milestones. His temperature is 98.2°F (36.8°C), blood pressure is 134/78 mmHg, pulse is 88/min, and respirations are 16/min. Physical exam reveals a well-appearing boy playing with a model train set. There is a small amount of downy hair in his axillary and pubic regions. His non-fasting laboratory results are shown below:

Serum:
Na+: 142 mEq/L
Cl-: 98 mEq/L
K+: 2.9 mEq/L
HCO3-: 30 mEq/L
Blood urea nitrogen (BUN): 16 mg/dL
Glucose: 102 mg/dL
Creatinine: 0.8 mg/dL

Elevated levels of which of the following molecules are the most likely cause of his high blood pressure?