2026 ICD-10-CM Diagnosis Code E05.31Thyrotoxicosis from ectopic thyroid tissue with thyrotoxic crisis or storm

ICD-10-CM Codes›E00–E89›E00-E07›E05

ICD-10-CM E05.31
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

E05.31 is a billable ICD-10-CM diagnosis code for thyrotoxicosis from ectopic thyroid tissue with thyrotoxic crisis or storm. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 643 through 645. Coders also document this condition as hyperthyroidism due to ectopic thyroid nodule. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Thyroid disorders.

Code Identity

ICD-10-CM Code
E05.31
Billable Status
Yes — Valid for Submission
Code Describes
Thyrotoxicosis from ectopic thyroid tissue with thyrotoxic crisis or storm
Short Description
Thyrotxcosis from ectopic thyroid tissue w thyrotoxic crisis
Parent Code
E05.3
Thyrotoxicosis from ectopic thyroid tissue

Code Classification

ChapterE00–E89Endocrine, nutritional and metabolic diseases
SectionE00-E07Disorders of thyroid gland
CategoryE05Thyrotoxicosis [hyperthyroidism]
This CodeE05.31Thyrotoxicosis from ectopic thyroid tissue with thyrotoxic crisis or storm

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Hyperthyroidism due to ectopic thyroid nodule
  • Hyperthyroidism due to hydatidiform mole with thyrotoxic crisis
  • Hyperthyroidism due to molar thyrotropin
  • Thyrotoxic crisis
  • Thyrotoxicosis due to ectopic thyroid nodule with crisis

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Hyperthyroidism(latent) (pre-adult) (recurrent)
      • due to ectopic thyroid tissue
        • with thyroid storm
    • Thyrotoxicosis(recurrent)
      • due to
        • ectopic thyroid nodule or tissue
          • with thyroid storm

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR END001
Thyroid disorders
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Hyperthyroidism

Hyperthyroidism, or overactive thyroid, happens when your thyroid gland makes more thyroid hormones than your body needs.

The full article covers:

  • What is hyperthyroidism?
  • What causes hyperthyroidism?
  • Who is at risk for hyperthyroidism?
  • What are the symptoms of hyperthyroidism?
  • What other problems can hyperthyroidism cause?
  • How is hyperthyroidism diagnosed?
  • What are the treatments for hyperthyroidism?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert E05.31 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
242.41 Thyrotox-ect nod w cris
Exact Match The mapping is direct, with no qualifiers.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About E05.31Overview

Is E05.31 (Thyrotoxicosis from ectopic thyroid tissue) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report thyrotoxicosis from ectopic thyroid tissue with thyrotoxic crisis or storm on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does E05.31 group to?

When thyrotoxicosis from ectopic thyroid tissue with thyrotoxic crisis or storm is the principal diagnosis on an inpatient stay, it groups to MS-DRG 643, 644, 645, with relative weights from 0.7683 to 1.6461 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of E05.31?

Under the General Equivalence Mappings, thyrotoxicosis from ectopic thyroid tissue with thyrotoxic crisis or storm converts to ICD-9-CM 242.41 (thyrotox-ect nod w cris). The mapping is a direct match.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.