ICD10BillableValid for clinical use
ICD-10 Code E21.1: Secondary hyperparathyroidism, not elsewhere classified
Reviewed by HealthAssure Clinical TeamUpdated 26 May 2026
What is this code?
ICD-10 codes are diagnosis classification codes used in healthcare records, reporting, coding workflows, and billing support. This code sits within the broader ICD-10 area for Endocrine, nutritional and metabolic diseases (E00-E89).
šClinical overview
This ICD-10 code is commonly used when documentation describes hyperparathyroidism or another parathyroid-gland disorder in the E21 family. The most accurate code depends on whether the record identifies primary, secondary, other, unspecified, or another specified parathyroid disorder.
When is it used?
- May be used when a clinician documents secondary hyperparathyroidism, not elsewhere classified in a patient's medical record.
- May appear in hospital records, claims, referrals, and clinical documentation.
- This code can be used as a clinically usable diagnosis entry in standardized coding workflows.
What it does not mean
- A code alone does not explain severity, treatment plan, or outcome.
- A medical code should not be treated as a substitute for a doctor's diagnosis or advice.
š©ŗClinical context
When commonly used
- Endocrinology, nephrology, primary-care, inpatient, and utilization-review workflows where hypercalcemia, parathyroid-hormone excess, or another parathyroid disorder is part of the active assessment.
- Coding workflows where the chart identifies primary versus secondary hyperparathyroidism or clarifies another specified parathyroid-gland disorder that changes final code specificity.
Common management context
- Evaluation often includes calcium, phosphorus, vitamin D, renal-function, and parathyroid-hormone review, symptom assessment for nephrolithiasis or bone effects, and endocrine follow-up planning.
- Documentation usually becomes more specific when the chart identifies primary versus secondary hyperparathyroidism, or clarifies another specified versus unspecified parathyroid-gland disorder.
- Specialist context already linked on this page includes Endocrinologist, General Physician.
šKey distinctions
Important notes
- This ICD-10 family captures hyperparathyroidism and closely related parathyroid-gland disorders rather than hypoparathyroidism, thyroid disease, or unrelated endocrine causes of calcium imbalance.
- Mechanism detail, such as primary, secondary, other, unspecified, or another specified parathyroid-gland disorder, drives final code specificity inside this family.
- Secondary hyperparathyroidism is coded separately from primary, other, and unspecified hyperparathyroidism because the documented cause or associated disease context changes code specificity.
- Documentation that describes hyperparathyroidism or another parathyroid-gland disorder is coded differently from hypoparathyroidism, thyroid disease, or other endocrine causes of calcium imbalance.
Important exclusions
- secondary hyperparathyroidism of renal origin (N25.81)
Related codes to consider
E21.0Primary hyperparathyroidism
Related hyperparathyroidism ICD-10 code; documentation often becomes more specific when the chart identifies primary versus secondary disease, or clarifies another specified versus unspecified parathyroid-gland disorder.
E21.2Other hyperparathyroidism
Related hyperparathyroidism ICD-10 code; documentation often becomes more specific when the chart identifies primary versus secondary disease, or clarifies another specified versus unspecified parathyroid-gland disorder.
E21.3Hyperparathyroidism, unspecified
Related hyperparathyroidism ICD-10 code; documentation often becomes more specific when the chart identifies primary versus secondary disease, or clarifies another specified versus unspecified parathyroid-gland disorder.
E21.4Other specified disorders of parathyroid gland
Related hyperparathyroidism ICD-10 code; documentation often becomes more specific when the chart identifies primary versus secondary disease, or clarifies another specified versus unspecified parathyroid-gland disorder.
Code hierarchy
chapter
4Endocrine, nutritional and metabolic diseases (E00-E89)
block
E20-E35Disorders of other endocrine glands
category
E21Hyperparathyroidism and other disorders of parathyroid gland
currentE21
Official coding notes
Excludes1 (do not code together)
- secondary hyperparathyroidism of renal origin (N25.81)
Where you may see this code
You may see this code in hospital records, discharge summaries, insurance claims, encounter documentation, referrals, or other healthcare billing and coding records.
Related specialists
EndocrinologistGeneral Physician
Related codes
Sibling codes
Coverage-related procedures and services
CPT 82306high
VITAMIN D; 25 HYDROXY, INCLUDES FRACTION(S), IF PERFORMED
Source: CMS coverage guidance
CPT 82652high
VITAMIN D; 1, 25 DIHYDROXY, INCLUDES FRACTION(S), IF PERFORMED
Source: CMS coverage guidance
CPT 83735high
MAGNESIUM
Source: CMS coverage guidance
CPT 00532high
ANESTHESIA FOR ACCESS TO CENTRAL VENOUS CIRCULATION
Source: CMS coverage guidance
CPT 01420high
ANESTHESIA FOR ALL CAST APPLICATIONS, REMOVAL, OR REPAIR INVOLVING KNEE JOINT
Source: CMS coverage guidance
CPT 01730high
ANESTHESIA FOR ALL CLOSED PROCEDURES ON HUMERUS AND ELBOW
Source: CMS coverage guidance
Mapped diagnoses and classifications
SNOMED_CT 78625002high
Hyperparathyroidism due to intestinal malabsorption
Source: SNOMED International ICD-10 map
SNOMED_CT 47445009high
Hyperparathyroidism due to vitamin D deficiency
Source: SNOMED International ICD-10 map
SNOMED_CT 91478007high
Secondary hyperparathyroidism
Source: SNOMED International ICD-10 map
SNOMED_CT 89471000119102high
Secondary hyperparathyroidism of nonrenal origin
Source: SNOMED International ICD-10 map
Coding guidelines
Compatibility
Legacy and official ICD code match exactly.
Legacy codes
E21.1
Common synonyms
Secondary hyperparathyroidism, not elsewhere classified
Frequently asked questions
About this content
This page is prepared by HealthAssure's clinical team using official coding standards from ICD-10. AI tools assist with drafting explanations, which are then reviewed and verified by healthcare professionals for accuracy. This content is for informational purposes and does not replace professional medical advice. Meet our team.