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 deficiency
  • Tertiary—also occurs in patients with 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
  • Familial hyperparathyroidism
  • Multiple endocrine neoplasia (MEN)
  • Parathyroid cancer—rare

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 gland is the main risk factor for tertiary hyperparathyroidism.