Calcium is an essential mineral that mainly plays an important role in maintaining the integrity of bones and teeth. Calcium is also needed by the heart, nerves, and blood-clotting systems to effectively work (1). Different regulatory processes that occur in the bones, gut, and kidneys influence blood calcium levels; but the hormones, parathyroid hormones and calcitonin, are the two main agents responsible in calcium homeostasis. Blood calcium levels must be maintained within narrow limits for the normal processes of muscle contraction and membrane potentials to occur (2).
How is Calcium maintained in the blood?
Parathyroid hormone
As stated, the parathyroid hormone
and calcitonin both help regulate
blood calcium levels. The Parathyroid
hormone (PTH) is produced by
the parathyroid gland, which is located on the back of the thyroid gland in the throat. PTH is only
released whenever blood calcium
levels are low.
- This hormone stimulates the osteoclasts, a type of bone cell, to break down bone that will then result to the release of calcium into the bloodstream.
- PTH also increases blood calcium levels by heightening the amount of calcium resorbed by the kidneys before excretion in to urine.
- PTH elevates calcium levels by triggering the formation of calcitriol, the biologically active form of Vitamin D, which increases absorption of dietary calcium through the intestines (3).
Calcitonin
On
the other hand, calcitonin is a
hormone released by the parafollicular
cells of the thyroid gland that acts in opposition to PTH.
- Calcitonin inhibits osteoclasts, slowing the breakdown of bone; and stimulates osteoblasts, a bone cell that is responsible in bone formation. The process results in calcium being added to the bones to promote structural integrity. This in turn lowers calcium release that will in time, lowers blood calcium concentration.
- The hormone also increases excretion of calcium in the urine that will further contribute to the decrease of blood calcium levels (3).
In short, The Parathyroid Hormone (PTH) increases blood calcium levels
while Calcitonin decreases blood calcium levels.
References:
(1) Calcium
[Internet]. [Place of publication unknown]: WebMD.com; [cited 2015 Feb 25].
Available from: http://www.webmd.com/vitamins-supplements/ingredientmono-781-calcium.aspx?activeingredientid=781&acti
veingredientname=calcium
(2) Miller J. Hormones
That Regulate Blood Calcium Levels [Internet]. [Place of publication unknown]:
Livestrong.com; [updated 2013 Oct 23; cited 2015 Feb 25]. Available from: http://www.livestrong.com/article/110719-hormones-regulate-blood-calcium-levels/
(3) Boundless. “Hormonal
Control of Blood Calcium Levels.” Boundless Biology. Boundless, 03 Jul. 2014.
Retrieved 28 Feb. 2015 from
https://www.boundless.com/biology/textbooks/boundless-biology-textbook/the
-endocrine-system-37/regulation-of-body-processes-212/hormonal-control-of-blood-calcium-levels-800-12036/
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