An acute or chronic dysfunction of the body's normal regulatory feedback mechanisms for parathyroid hormone.

• Primary:
  • Intrinsic gland dysfunction causing excessive parathyroid hormone (PTH) secretion
• Secondary:
  • Gland hyperactivity that is a response to hypocalcemia or vitamin D deficiency
• Tertiary:
  • Autonomous hyperfunction in the setting of long standing secondary hyperparathyroidism (HPT)