In CKD-related secondary hyperparathyroidism, which histologic change is commonly observed in the parathyroid glands?

• A. Parathyroid atrophy
• B. Parathyroid adenoma
• C. Parathyroid hyperplasia
• D. No histologic change

Answer: (C)

Chronic stimulation from CKD causes the parathyroid glands to multiply their cells and enlarge, so the typical histology shows parathyroid hyperplasia. In CKD, phosphate retention, low calcium, and reduced active vitamin D drive PTH secretion continuously, and the glands respond by increasing cell number and mass. Early on this is diffuse hyperplasia across all glands, and with longer disease it can become nodular hyperplasia. This pattern contrasts with primary hyperparathyroidism, where a single gland often harbors an adenoma. Atrophy or a lack of histologic change wouldn’t reflect the ongoing stimulus-driven enlargement seen in secondary hyperparathyroidism. Therefore, hyperplasia is the common histologic change.