A 52-year-old woman with resistant hypertension (BP 160/100 mmHg despite amlodipine and lisinopril) undergoes screening for secondary causes. Plasma renin activity is markedly suppressed (0.3 ng/mL/hr; normal 0.5–2.0), and 24-hour urinary aldosterone is elevated at 18 μg/day (normal <12). Serum potassium is 3.2 mEq/L. Abdominal CT shows a 2 cm left adrenal mass. Which of the following best explains the suppressed renin activity in this patient?