This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
Which among the following is the most frequent manifestation of MEN 1? 
Select and explain. 
A. Parathyroid hyperplasia, B. Pituitary adenoma, C. Adrenal adenoma, D. Bronchial carcinoids
A: Parathyroid hyperplasia
Answer: A: Parathyroid hyperplasia 
Explanation: MEN 1 is an autosomal dominant disorder due to a defect in 11q13, which encodes for a 610-amino-acid nuclear protein, menin. Patients with MEN1 develop hyperparathyroidism due to parathyroid hyperplasia in 95-100% of cases, pituitary adenomas in 54-80%, adrenal adenomas in 27-36%, bronchial carcinoids in 8%. Ref: Harrisons Principles of Internal Medicine, 18th Edition, Page 3060.