E31.21
BillableMultiple endocrine neoplasia [MEN] type I
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is E31.21 an HCC code?
Yes. E31.21 maps to Other Significant Endocrine and Metabolic Disorders under the CMS-HCC V28 risk adjustment model (and Other Significant Endocrine and Metabolic Disorders under V24).
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
MEAT Criteria for E31.21
For E31.21to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically — it has to be re-documented and supported each calendar year.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed E31.21 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
E31.21 is the ICD-10-CM diagnosis code for multiple endocrine neoplasia [men] type i. A hereditary condition where tumors develop in the pituitary gland, pancreas, and parathyroid glands, causing hormone imbalances. E31.21 sits in the ICD-10-CM chapter for endocrine, nutritional and metabolic diseases (e00-e89), within the section covering disorders of other endocrine glands (e20-e35).
Under the CMS-HCC V28 risk adjustment model, E31.21 maps to Other Significant Endocrine and Metabolic Disorders (HCC 51) with a community, non-dual, aged base RAF weight of 0.233. Under the older V24 model, E31.21 mapped to the same category but with a base RAF weight of 0.230 — V28 recalibrated weights across the entire model. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
Document specific tumors present (pituitary adenoma, gastrinoma, insulinoma, parathyroid adenoma) as secondary diagnoses. Because E31.21 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for E31.21 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Document specific tumors present (pituitary adenoma, gastrinoma, insulinoma, parathyroid adenoma) as secondary diagnoses
- •This is an inherited condition; consider coding family history if relevant to the encounter
Clinical Significance
Multiple endocrine neoplasia type I (Wermer syndrome) is an autosomal dominant condition caused by mutations in the MEN1 tumor suppressor gene, predisposing to tumors of the parathyroid glands (95%), pancreatic islet cells (40%), and anterior pituitary (30%). Primary hyperparathyroidism is usually the earliest manifestation, often presenting before age 30.
Documentation Requirements
- ✓Document MEN1 genetic testing results, which endocrine tumors are present (parathyroid adenoma, gastrinoma, insulinoma, prolactinoma), tumor sizes and locations on imaging, hormone levels for each affected gland, surgical history, and surveillance protocol for tumor screening.