In multiple endocrine neoplasia type 1, which endocrine lesion is present in the highest proportion of affected individuals and is usually the first manifestation?

• A Gastrin-producing pancreatic neuroendocrine tumour
• B Medullary carcinoma of the thyroid
• C Prolactin-secreting pituitary adenoma
• D Parathyroid hyperplasia involving multiple glands ✓

Explanation

Primary hyperparathyroidism from multiglandular parathyroid hyperplasia occurs in about 90 percent of MEN1 patients and is typically the earliest and most frequent manifestation. Gastrinomas occur in roughly 40 percent and prolactinomas in about 20 to 25 percent. Medullary thyroid carcinoma belongs to MEN2, driven by RET mutations, not MEN1, which involves the menin gene, so option B is categorically wrong for MEN1.

Reference: Williams Textbook of Endocrinology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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