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Hyperparathyroidism

Hyperparathyroidism is a topic covered in the 5-Minute Clinical Consult.

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Basics

Description

A dysfunction of the body’s normal regulatory feedback mechanisms resulting in excess production of parathyroid hormone (PTH)

  • Primary hyperparathyroidism (HPT): intrinsic parathyroid gland dysfunction resulting in excessive secretion of PTH with a lack of response to feedback inhibition by elevated calcium
  • Secondary HPT: excessive secretion of PTH in response to potential hypocalcemia and/or hyperphosphatemia. This is commonly caused by vitamin D deficiency or renal failure.
  • Tertiary HPT: autonomous hyperfunction of the parathyroid gland in the setting of long-standing secondary HPT

Epidemiology

Incidence
  • Predominantly postmenopausal females
  • Female > male (3:1)

Prevalence
Primary HPT is 1 in 500 to 1 in 1,000 in the United States.

Etiology and Pathophysiology

  • PTH is synthesized by the four parathyroid glands, which are located behind the four poles of the thyroid gland (locations can vary).
  • Ectopic (abnormal locations and most common is the thymus) or supernumerary glands (more than four glands)
  • PTH releases calcium from bone by osteoclastic stimulation (increasing bone resorption).
  • PTH increases reabsorption of calcium in the distal tubules of the kidneys.
  • PTH stimulates conversion of 25-hydroxycholecalciferol (25[OH]D) to 1,25-dihydroxycholecalciferol (1,25[OH]2D or active vitamin D) in the kidneys. 1,25(OH)2D increases calcium and phosphate absorption from the GI tract and kidneys, and stimulates osteoclastic activity and bone resorption.
  • Primary HPT: unregulated PTH production and release due to the loss of normal feedback control by extracellular calcium, causing increase in serum calcium
    • Solitary adenoma (80–85%)
    • Diffuse hyperplasia (10–15%) of the four parathyroid glands, either sporadically or in association with multiple endocrine neoplasia (MEN) types I or II
    • Parathyroid carcinoma (<1%), a very rare and severe form
  • Secondary HPT: adaptive parathyroid gland hyperplasia and hyperfunction
    • Dietary: vitamin D or calcium deficiency
    • Chronic renal disease resulting in the following:
      • Renal parenchymal loss causing hyperphosphatemia
      • Impaired calcitriol production causing hypocalcemia
      • General skeletal and renal resistance to PTH
  • Tertiary HPT: autonomous oversecretion of PTH following prolonged parathyroid stimulation

Genetics
  • MEN types I and II: Patients with multiple gland hyperplasia in the absence of renal disease should be screened for MEN-I gene mutation.
  • Neonatal severe primary HPT
  • HPT—jaw tumor syndrome
  • Familial hypocalciuric hypercalcemia (FHH)
  • Familial isolated HPT

Risk Factors

Chronic kidney disease, increasing age, poor nutrition, radiation, and/or family history

General Prevention

Adequate intake of calcium and vitamin D may help prevent secondary HPT.

Commonly Associated Conditions

  • Vitamin D deficiency
  • Chronic renal failure
  • MEN syndromes types I and II

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Citation

Stephens, Mark B., et al., editors. "Hyperparathyroidism." 5-Minute Clinical Consult, 27th ed., Wolters Kluwer, 2019. Medicine Central, im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/117547/1.2/Hyperparathyroidism.
Hyperparathyroidism. In: Stephens MB, Golding J, Baldor RA, et al, eds. 5-Minute Clinical Consult. 27th ed. Wolters Kluwer; 2019. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/117547/1.2/Hyperparathyroidism. Accessed June 27, 2019.
Hyperparathyroidism. (2019). In Stephens, M. B., Golding, J., Baldor, R. A., & Domino, F. J. (Eds.), 5-Minute Clinical Consult. Available from https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/117547/1.2/Hyperparathyroidism
Hyperparathyroidism [Internet]. In: Stephens MB, Golding J, Baldor RA, Domino FJ, editors. 5-Minute Clinical Consult. Wolters Kluwer; 2019. [cited 2019 June 27]. Available from: https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/117547/1.2/Hyperparathyroidism.
* Article titles in AMA citation format should be in sentence-case
TY - ELEC T1 - Hyperparathyroidism ID - 117547 ED - Stephens,Mark B, ED - Golding,Jeremy, ED - Baldor,Robert A, ED - Domino,Frank J, BT - 5-Minute Clinical Consult, Updating UR - https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/117547/1.2/Hyperparathyroidism PB - Wolters Kluwer ET - 27 DB - Medicine Central DP - Unbound Medicine ER -