Hyperparathyroidism is when the body makes too much parathyroid hormone (PTH). The parathyroid glands make PTH which help to keep calcium levels in balance.

Hyperparathyroidism may be:

  • Primary—a benign tumor of the parathyroid gland that makes too much PTH (most common form)
  • Secondary—occurs in patients with long-standing kidney failure or a vitamin D deficient state
  • Tertiary—also occurs in patients with very long-standing kidney failure and dialysis

Thyroid and Parathyroid Glands: Posterior (Back) View
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Primary hyperparathyroidism may be caused by:

  • Noncancerous tumor in the parathyroid gland (most common cause)
  • Parathyroid cancer (very rare)
  • Familial hyperparathyroidism
  • Multiple endocrine neoplasia (MEN)

Secondary hyperparathyroidism may be caused by:

  • Vitamin D deficiency (due to inadequate dietary intake, lack of sunlight exposure, or malabsorption condition like celiac disease)
  • Kidney failure or other medical problems that make the body resistant to the action of the parathyroid hormone
  • Enlargement of the parathyroid glands—common cause

Enlargement of the parathyroid gland is the main risk factor for tertiary hyperparathyroidism.