Introduction: Primary hyperaldosteronism is a leading cause of secondary arterial hypertension, affecting approximately 10% to 20% of the hypertensive population worldwide and in Brazil. This condition involves excessive aldosterone production due to factors such as adrenal adenoma, hyperplasia, or, less commonly, adrenal carcinoma and familial hyperaldosteronism. This study reports a case of resistant hypertension secondary to aldosterone-producing adenoma. Clinical Case: A 70-year-old male patient presented with episodes of dizziness, syncope, cramps, and asthenia. His medical history included resistant hypertension for over 30 years, despite treatment with five classes of antihypertensive medications. Additionally, he had a history of dyslipidemia, type 2 diabetes mellitus, non-dialysis chronic renal failure, and obstructive coronary arterydisease. Physical examination showed a BMI of 29 kg/m² (overweight), mean blood pressure of 140/90 mmHg (right arm) and 150/100 mmHg (left arm), and palpable nodules in both thyroid lobes, classified as Bethesda V based on aspiration cytopathology. Subsequently, he underwent total thyroidectomy and lymph node dissection. Laboratory tests revealed high plasma aldosterone levels with suppressed renin and an elevated aldosterone-renin ratio, raising suspicion of primary hyperaldosteronism. This diagnosis was confirmed by a computed tomography scan, which identified a 1.2 cm nodule in the right adrenal gland consistent with an adenoma. The patient underwent unilateral laparoscopic adrenalectomy. Two years post-surgery, the patient’s blood pressure was well-controlled with three antihypertensive medications, and his blood sugar, aldosterone, and renin levels were normal. Discussion and Conclusion: Most patients undergoing unilateral adrenalectomy for aldosterone-producing adenomas experience significant clinical improvement. Early screening and diagnosis of primary hyperaldosteronism are crucial for effective management, reducing the risk of complications in the cardiovascular and renal systems.