E21.0 Primary hyperparathyroidism

Billable ICD-10-CM code, FY2026.

Applicable to

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

Applies from E21 Hyperparathyroidism and other disorders of parathyroid gland

Excludes1 (never code together)

• adult osteomalacia (M83.-)
• ectopic hyperparathyroidism (E34.2)
• hungry bone syndrome (E83.81)
• infantile and juvenile osteomalacia (E55.0)

Excludes2 (not included here)

• familial hypocalciuric hypercalcemia (E83.52)

Risk adjustment (HCC)

• CMS-HCC V22: HCC 23 — Other Significant Endocrine and Metabolic Disorders
• RxHCC V08: HCC 43 — Pituitary, Adrenal Gland, and Other Endocrine and Metabolic Disorders
• ESRD V24: HCC 23

MS-DRG index

Defines the logic of DRG(s) 643-645 in MDC 10.

Approximate ICD-9-CM (GEMs)

• 252.01 Primary hyperparathyroidism

Code annotations containing back-references to E21.0

Back-references to E21.0

• Type 1 Excludes: E83.5 Disorders of calcium metabolism ("hyperparathyroidism (E21.0-E21.3)")
• Code First: G73.7 Myopathy in diseases classified elsewhere ("hyperparathyroidism (E21.0, E21.3)")
• Code First: M49 Spondylopathies in diseases classified elsewhere ("osteitis fibrosa cystica (E21.0)")
• Type 1 Excludes: M85.6 Other cyst of bone ("osteitis fibrosa cystica generalisata [von Recklinghausen's disease of bone] (E21.0)")

Back-references to E21

• Type 1 Excludes: E83 Disorders of mineral metabolism ("parathyroid disorders (E20-E21)")
• Code First: G63 Polyneuropathy in diseases classified elsewhere ("endocrine disease, except diabetes (E00-E07, E15-E16, E20-E34)")
• Code First: M14.8 Arthropathies in other specified diseases classified elsewhere ("hyperparathyroidism (E21.-)")

Diagnosis Index entries for E21.0

• Curvature › spine (acquired) (angular) (idiopathic) (incorrect) (postural) › due to or associated with › osteitis › fibrosa cystica
• Disease, diseased › osteofibrocystic
• Enlargement, enlarged › parathyroid (gland)
• Hyperparathyroidism › primary
• Hyperplasia, hyperplastic › parathyroid (gland)
• Hypertrophy, hypertrophic › parathyroid (gland)
• Osteitis › fibrosa NEC › cystica (generalisata)
• Osteitis › fibrosa NEC › osteoplastica
• Osteitis › parathyroid
• Recklinghausen disease › bones
• Von Recklinghausen › disease (neurofibromatosis) › bones

Nearby codes

• E21 Hyperparathyroidism and other disorders of parathyroid gland
• E21.0 Primary hyperparathyroidism (this code)
• 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