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E21.0 ICD-10-CM Code: Primary hyperparathyroidism

Billing Status: YES. This is a valid, specific, and billable ICD-10-CM reference.

Coding at a Glance

Tabular directives
2 inclusion terms · 6 Excludes1 · 1 Excludes2
Risk adjustment
CMS-HCC V22 category 23 · RxHCC V08 category 43

Inpatient Payment Groups (MS-DRG)

Potential MS-DRG participation — not a DRG assignment.

MS-DRGs this diagnosis helps define, as principal or secondary, per the CMS ICD-10-CM/PCS MS-DRG Definitions Manual v43, Appendix B.

  • MS-DRG 643 — ENDOCRINE DISORDERS WITH MCC (MDC 10)
  • MS-DRG 644 — ENDOCRINE DISORDERS WITH CC (MDC 10)
  • MS-DRG 645 — ENDOCRINE DISORDERS WITHOUT CC/MCC (MDC 10)

A diagnosis appearing in a group's logic does not by itself determine the DRG assigned to a stay; the grouper uses the full claim.

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for E21.0 in the official ICD-10-CM tabular list, quoted as published.

Source: CMS/CDC — ICD-10-CM Tabular ListRelease: FY2026Effective: October 1, 2025

Notes without a marker are published on E21.0 itself; “inherited from” names the category or block whose note applies here.

Inclusion Terms

Alternative terms the tabular list files under this code.

  • Hyperplasia of parathyroid
  • Osteitis fibrosa cystica generalisata [von Recklinghausen's disease of bone]

Excludes1 — Not Coded Here

Conditions generally not reported together with this code (Excludes1) -- an error unless the two conditions are documented as unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).

Excludes2 — Not Included Here

Conditions not covered by this code, but which may be reported alongside it when both are present.

Source: inherited from E21

Coder workflow for E21.0

MedCoder structured workflow — derived from this code’s own official record

Before you code E21.0

  1. Check the Excludes1 note: if the documentation supports a condition named there, do not simply proceed with E21.0. Excludes1 conditions are not reported together with this code unless the record shows they are unrelated (Guidelines I.A.12.a).

    See the official tabular notes

Choose the right path

  1. Does the documentation support a condition named in E21.0’s Excludes1 note?
    Yes → Do not simply proceed: review the excluded code. Both are reported only when the record shows the two conditions are unrelated.
    No → Continue.

    ReviewM83, E34.2, E83.81, E55.0, N64.3, N62

Consider E21.0. Then confirm the code is valid for the date of service in the Verify section.

Documentation check

The provider’s diagnostic statement
Codes are assigned from the provider’s documented diagnosis, not from clinical criteria, test values or a medication list (Guidelines I.A.19).

Official instructions as workflow

  • Excludes1 — check before selecting E21.0(6 notes)

    Coding workflow: If the documentation supports a condition named in this note, do not simply proceed with E21.0: the two are not reported together. The one exception is when the record shows the two conditions are unrelated to each other.

    CompareM83, E34.2, E83.81, E55.0, N64.3, N62

    See the official tabular notes · Guidelines I.A.12.a

  • Excludes2 — not part of E21.0(1 note)

    Coding workflow: The conditions named in this note are not included in E21.0. When the record documents both, both may be reported; the note is a boundary, not a prohibition.

    CompareE83.52

    See the official tabular notes · Guidelines I.A.12.b

Coding decision scenarios

Pattern scenarios for this code’s structure — decision rules, not clinical cases

Documentation: Both the condition E21.0 describes and a condition named in its Excludes1 note are documented for the same encounter.

Coding question: Can both codes be reported?

Path: Review the Excludes1 note and the excluded code, and look for a provider statement on whether the two conditions are related.

Reason: Excludes1 means the two are not coded together; the exception is when the record shows the conditions are unrelated to each other (Guidelines I.A.12.a).

ReviewM83, E34.2, E83.81, E55.0, N64.3, N62

Every row is derived from this code’s own record — its title, tabular notes, 7th-character family and same-category siblings — with fixed MedCoder wording; nothing is inferred about a patient. The official notes and guideline text are in the sections each row links to, and they control.

Code Overview

Primary hyperparathyroidism is a billable ICD-10-CM diagnosis code (E21.0).

MedCoder summary Summary composed by MedCoder from this code's official ICD-10-CM record. The tabular instructional notes themselves appear verbatim below.

Indexed Clinical Terms (11)

Official source data — entries quoted as published, in the Index’s own lookup phrasing

Clinical term phrases from the official ICD-10-CM Index to Diseases and Injuries that map to this code. These are alphabetic-index entries shown as the Index writes them — lookup phrasing, not necessarily the wording of a final diagnosis.

Verify Before Coding

  • No Medicare Code Editor or MS-DRG Definitions Manual restrictions apply to this code.

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim in Claim Check.

Relationships & Classification

MedCoder structured relationships — computed from published CMS and AHRQ datasets

Other codes that name E21.0 or its code family, from the CMS ICD-10-CM tabular instructional notes. Tabular-note edges are stored at the code family level that carries each note.

Referenced by 3 Excludes1 notes across 2 chapters: E83 — Disorders of mineral metabolism (via E21.-), E83.5 — Disorders of calcium metabolism, M85.6 — Other cyst of bone.

These codes’ tabular lists mark this diagnosis as mutually exclusive — not reported together unless the conditions are documented as unrelated.

Referenced by 4 Code First instructions across 2 chapters: G63 — Polyneuropathy in diseases classified elsewhere (via E21.-), G73.7 — Myopathy in diseases classified elsewhere, M14.8 — Arthropathies in other specified diseases classified elsewhere (via E21.-), M49 — Spondylopathies in diseases classified elsewhere.

Each of these codes carries a Code First note naming this condition — when that code is reported, THIS code is sequenced first, ahead of it.

MS-DRG Grouper Relationships (FY2026)

Potential MS-DRG participation — not a DRG assignment.

FY2026 MS-DRG: not on the CMS CC/MCC list — as a secondary diagnosis this code does not change MS-DRG severity for that release.

Named in the grouper logic of 3 MS-DRGs: DRG 643 (MDC 10), DRG 644 (MDC 10), DRG 645 (MDC 10).

From the CMS MS-DRG Definitions Manual (Appendices B and C). Actual DRG assignment depends on the complete claim.

Clinical classification (AHRQ CCSR):END015 — Other specified and unspecified endocrine disorders (default).

Clinical Classifications Software Refined (CCSR) for ICD-10-CM Diagnoses. Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality.

Related Codes

Same clinical category (CCSR)

AHRQ's Clinical Classifications Software groups these diagnoses under the same clinical category (Other specified and unspecified endocrine disorders).

E20.0 — Idiopathic hypoparathyroidism, E20.1 — Pseudohypoparathyroidism, E20.8 — Other hypoparathyroidism, E20.810 — Autosomal dominant hypocalcemia, E20.811 — Secondary hypoparathyroidism in diseases classified elsewhere, E20.812 — Autoimmune hypoparathyroidism, E20.818 — Other specified hypoparathyroidism due to impaired parathyroid hormone secretion, E20.819 — Hypoparathyroidism due to impaired parathyroid hormone secretion, unspecified, E20.89 — Other specified hypoparathyroidism, E20.9 — Hypoparathyroidism, unspecified, E21.1 — Secondary hyperparathyroidism, not elsewhere classified, E21.2 — Other hyperparathyroidism, E21.3 — Hyperparathyroidism, unspecified, E21.4 — Other specified disorders of parathyroid gland, E21.5 — Disorder of parathyroid gland, unspecified, E24.1 — Nelson's syndrome, E24.2 — Drug-induced Cushing's syndrome, E24.3 — Ectopic ACTH syndrome, E24.4 — Alcohol-induced pseudo-Cushing's syndrome, E24.8 — Other Cushing's syndrome, +83 more

Same Index main term, other category

The ICD-10-CM Index to Diseases and Injuries files this code under the main terms “Hypertrophy, hypertrophic”, “Hyperplasia, hyperplastic”, “Enlargement, enlarged”, …; these codes share that main term but sit in a different category of the Tabular List.

D49.89 — Neoplasm of unspecified behavior of other specified sites (deformans, in, neoplastic disease, multiple sites), D49.9 — Neoplasm of unspecified behavior of unspecified site (deformans, in, neoplastic disease), D75.89 — Other specified diseases of blood and blood-forming organs (erythroid), D86.89 — Sarcoidosis of other sites (tuberculosa, cystica), E07.0 — Hypersecretion of calcitonin (C-cell, thyroid), E16.1 — Other hypoglycemia (pancreatic islet cells, beta), E16.3 — Increased secretion of glucagon (pancreatic islet cells, alpha, with excess, glucagon), E16.4 — Increased secretion of gastrin (pancreatic islet cells, alpha, with excess, gastrin), E16.8 — Other specified disorders of pancreatic internal secretion (pancreatic islet cells, alpha), E16.9 — Disorder of pancreatic internal secretion, unspecified (pancreatic islet cells), E23.6 — Other disorders of pituitary gland (pituitary), E25.0 — Congenital adrenogenital disorders associated with enzyme deficiency (adrenal, congenital), E25.9 — Adrenogenital disorder, unspecified (adrenal, with, virilization), E27.5 — Adrenomedullary hyperfunction (adrenomedullary), E27.8 — Other specified disorders of adrenal gland (adrenal), E32.0 — Persistent hyperplasia of thymus (thymus), E64.3 — Sequelae of rickets (spine, sequelaeof rickets), E65 — Localized adiposity (fat pad), G60.0 — Hereditary motor and sensory neuropathy (spine, due to or associated with, Charcot-Marie-Tooth disease), G71.09 — Other specified muscular dystrophies (pseudomuscular), +169 more

Lab tests where this diagnosis supports Medicare coverage (NCD)

Medicare's National Coverage Determination (NCD) program lists this diagnosis as medical justification for these lab tests.

Gamma-glutamyl Transferase (GGT) Test

Contextual Map

Every relationship of E21.0 in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Run E21.0 with these 7 related codes in Claim Check

Hierarchy

Referenced by Excludes1 notes

Referenced by Code First instructions

Clinical classification (CCSR)

MS-DRG Grouper

MDC crossing

  • MDC 10 — Endocrine, Nutritional and Metabolic Diseases and Disorders[MDC crossing]: “Endocrine, Nutritional and Metabolic Diseases and Disorders — the grouper's crossing between diagnoses and procedures: a principal diagnosis sets the MDC, and same-MDC procedures move the stay to its surgical DRGs. 5,008 same-MDC procedures group here; browse them on the MDC page.”— CMS MS-DRG Definitions Manual · FY2026

Index entries (11)

  • Curvature, spine (acquired) (angular) (idiopathic) (incorrect) (postural), due to or associated with, osteitis, fibrosa cystica[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Disease, diseased, osteofibrocystic[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Enlargement, enlarged, parathyroid (gland)[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Hyperparathyroidism, primary[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Hyperplasia, hyperplastic, parathyroid (gland)[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Hypertrophy, hypertrophic, parathyroid (gland)[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Osteitis, fibrosa NEC, cystica (generalisata)[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Osteitis, fibrosa NEC, osteoplastica[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • and 3 more

Nearest codes

Change history

  • FY2016 — In the code set at ICD-10-CM adoption [Change history]— CMS release files (code change ledger) · icd10cm-fy2016

Sources for this page

Codes, titles, notes, index terms and mappings on this page are transcribed from the datasets below. Relationships MedCoder computed and text MedCoder wrote are labelled where they appear.

Code, title, tabular notes and index terms Official source data
CMS/CDC ICD-10-CM FY2026 tabular list, index and tables, effective October 1, 2025 Release, file and checksum · Publisher’s page
Claim edits Official source data
CMS Definitions of Medicare Code Edits — v43.1 (April 2026) Release, file and checksum · Publisher’s page
Inpatient payment groups Official source data
CMS MS-DRG Definitions Manual (incl. Appendix B diagnosis index, Appendix C CC/MCC list, Appendix E procedure index) and IPPS Final Rule tables — v43 Release, file and checksum · Publisher’s page
Change history and date-of-service validity Official source data
CMS ICD-10-CM release addenda, ingested release by release into the change ledger Release, file and checksum · Publisher’s page
Comparisons, relationships and the contextual map MedCoder structured relationship
Computed by MedCoder from the tabular notes and tables above; every derived relationship is marked as derived where it appears
Summary and FAQ answers MedCoder explanation
Written by MedCoder to explain the sources above: drafted with AI assistance, checked by a person against the release files, and labelled as MedCoder text where it appears. Not official text.

Labels on this page: Official source data · MedCoder structured relationship · MedCoder explanation. How to read the labels · All data sources and release dates

Cite this page

Reference this page in a research guide, syllabus or article. The release is included because code content changes each year.

MedCoder.ai. "E21.0 — Primary hyperparathyroidism." ICD-10-CM FY2026. https://medcoder.ai/icd10/code/e21.0-primary-hyperparathyroidism

Change history

  • FY2016 — October 1, 2015
    In the code set at ICD-10-CM adoption
    Primary hyperparathyroidism

No changes since FY2016 — additions, deletions, description changes and billable-status changes are tracked through FY2027 (effective October 1, 2026), and none are recorded for this code. Note changes are tracked from FY2027 only.

Nearest Codes in This Family

Official ICD-10-CM classifications closest to E21.0 in its code family, with their registry titles.

View all codes in the E21 family