ICD-10 Code E31.21 – Multiple endocrine neoplasia [MEN] type I (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code E31.21 – Multiple endocrine neoplasia [MEN] type I
What it is
E31.21 identifies multiple endocrine neoplasia type I, an inherited syndrome that predisposes you to tumors in several hormone-producing glands. It is used when the diagnosis is documented, not for a single isolated endocrine tumor.
Clinical signs
Clinical features vary; refer to documentation. Commonly documented findings include parathyroid, pituitary, and pancreatic neuroendocrine tumors, often with a family history of MEN1 or early-onset endocrine disease.
When to use this code
Use this code when the provider clearly documents MEN type I, MEN1 syndrome, or multiple endocrine neoplasia type 1. It may also apply when the chart confirms a hereditary endocrine tumor syndrome and the diagnosis is established. Do not use it for suspicion alone.
Do not use for
Do not use this code for isolated endocrine tumors without MEN1 documentation. If the record only says “rule out” MEN1 or gives another MEN type, check documentation.
Coding tip
Confirm the exact syndrome type in the assessment, problem list, or genetics note before assigning E31.21.