The remaining 20% of primary hyperparathyroidism cases are due to which condition?

• A. Parathyroid hyperplasia
• B. Single adenoma
• C. Carcinoma
• D. Adenoma in all glands

Answer: (A)

In primary hyperparathyroidism, the distribution of causes matters for both diagnosis and management. While a solitary parathyroid adenoma is the most common culprit, about one-fifth of cases come from parathyroid hyperplasia, where multiple glands enlarge and secrete excess PTH. This multisite overactivity explains the remaining percentage of PHPT cases. Parathyroid carcinoma is rare and would be an unusual cause for a sizable portion of cases, and the notion of an adenoma occurring in all glands isn’t how PHPT typically presents. Clinically, recognizing hyperplasia matters because surgical treatment often involves removing or reducing multiple glands (with subtotal or total parathyroidectomy and possible autotransplantation) rather than just removing a single adenoma.