Sign Up for a Free Account

This is an image preview.
Start a Free Account
to view the full image.

Sign Up for a Free Account For information on discounts, see Plans & Pricing

  • Nearly 3,000 illustrations, including video clips of neurologic disorders.

  • Every article is reviewed by our esteemed Editorial Board for accuracy and currency.

  • Full spectrum of neurology in 1,200 comprehensive articles.

  • Listen to MedLink on the go with Audio versions of each article.

Calcium regulation

Calcium is transported through the bloodstream as dissolved divalent cations (Ca2+) or bound to proteins (eg, serum albumin). Calcium levels are tightly regulated. Parathyroid hormone, secreted by the parathyroid gland, regulates (1) the resorption of calcium from bone (the major calcium storage site in the body); (2) reabsorption in the kidney back into circulation; and (3) increases in the activation of vitamin D3 to calcitriol. Calcitriol, the active form of vitamin D3, promotes absorption of calcium from the intestines and the mobilization of calcium ions from bone matrix. Calcitonin, which is secreted from the parafollicular cells of the thyroid gland, also affects calcium levels by opposing parathyroid hormone, but its physiological significance in humans is limited. (Image by Mikael Häggström (2009). (Courtesy of Wikimedia Commons. Public domain.)

Related Article

Related Media

Associated Disorders

  • Acute and chronic renal failure
  • Endocrine disorders
  • Familial hypocalciuric hypercalcemia
  • Granulomatous disorders
  • Infantile hypercalcemia (Williams syndrome)
  • Malignancy
  • Milk-alkali syndrome
  • Primary hyperparathyroidism