Conn syndrome

A 44-year-old man comes to his physician complaining of muscle weakness and headaches for the past 2 months. He is a construction worker and has found it difficult to lift large objects during the job. The patient has no significant past medical history, but he states his blood pressure was “high” at a recent health fair. Temperature is 37.0°C (98.6°F), pulse is 82/min, and blood pressure is 165/92 mm Hg. Physical examination reveals no abnormalities. Laboratory testing reveals the following findings:

 

Laboratory Value	Result
Serum
Sodium	147 mEq/L
Potassium	2.9 mEq/L
Chloride	105 mEq/L
HCO3-	32 mEq/L
Creatinine	0.6 mg/dL
Glucose	94 mg/dL

Serum renin levels are decreased. Which of the following is the most likely cause of this patient’s condition?