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E21.0 — Primary hyperparathyroidism
E21.0
What this code means
Primary hyperparathyroidism: an overactive parathyroid gland releases too much parathyroid hormone, raising blood calcium.
Also called: primary hyperparathyroidism.
When this code is used
Used for primary hyperparathyroidism.
Where it sits in ICD-10-CM
Code E21.0 belongs to Chapter 4: Endocrine, nutritional and metabolic diseases, which covers codes E00–E89 in the FY2027 ICD-10-CM tabular list. The official description above is copied verbatim from the CDC/NCHS FY2027 code file.
Related symptoms
Frequently asked questions
What is ICD-10-CM code E21.0?
E21.0 is the ICD-10-CM diagnosis code for “Primary hyperparathyroidism”. Primary hyperparathyroidism: an overactive parathyroid gland releases too much parathyroid hormone, raising blood calcium.
When is code E21.0 used?
Used for primary hyperparathyroidism. It belongs to Chapter 4 of ICD-10-CM (Endocrine, nutritional and metabolic diseases).
This guide explains ICD-10-CM codes in plain language for patients, students and other readers. It is educational information only — not coding, billing or medical advice. The code recorded for any real encounter is assigned from the full clinical documentation by the treating team and qualified coders, and only they can decide which code fits a specific case.