This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Medicine
[{'content': 'A 25-year-old lady has put on weight and has oligomenorrhea followed by amenorrhea for 8 months. The blood pressure is 160/100 mm of Hg. Which of the following is the most appropriate investigation? \nSelect and explain. \nA. Serum electrolytes, B. Plasma cortisol, C. Plasma testosterone and USG, D. T3, T4 and TSH', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. B. Plasma cortisolThe given clinical situation suggests a diagnosis of Cushing's which is diagnosed by Cortisol levels.* Weight gain with oligomenorrhea points to Cushing's syndrome.* Cortisol inhibits gonadotropin release that explains amenorrhea.* Hypertension in these patients is secondary to increased cortisol that has some mineralocorticoid activity also.", 'role': 'assistant'}]