calcitonin

Biology

(noun)

a hormone, secreted by parenchymal cells, that regulates calcium and phosphate metabolism

Related Terms

  • parathyroid hormone
  • hyperparathyroidism
  • hypoparathyroidism
  • calcitriol
  • osteoclast
  • osteoblast
Physiology

(noun)

A hormone that is produced primarily by the parafollicular cells of the thyroid. It acts to reduce blood calcium (Ca2+), opposing the effects of parathyroid hormone.

Related Terms

  • thyroid follicle
  • thyroid-stimulating hormone
  • parathyroid gland
  • parathyroid hormone
  • thyrotropin-releasing hormone
  • vitamin D

Examples of calcitonin in the following topics:

  • Thyroid Gland

    • The thyroid gland, the largest endocrine gland, is responsible for the production of the hormones T3, T4, and calcitonin.
    • Another hormone produced by the thyroid gland, thyrocalcitonin, or calcitonin, decreases the concentration of calcium in the blood.
    • Calcitonin is produced by parafollicular cells of the thyroid, either releasing hormones or inhibiting hormones.
    • Calcitonin functions to help regulate calcium concentrations in body fluids.
    • The location of the thyroid gland is in the neck below the larynx and in front of the trachea; it is the largest endocrine gland in the body, producing T3, T4, and calcitonin.
  • Action of Thyroid Hormones

    • The primary function of the thyroid is to produce the hormones triiodothyronine (T3), thyroxine (T4), and calcitonin.
    • Calcitonin is another hormone released by the thyroid gland that is responsible for modulating blood calcium levels in conjunction with parathyroid hormone, which is released from the parathyroid.
  • Bone and Calcium Homeostasis

    • Calcitonin stimulates incorporation of calcium in bone.
    • When blood calcium concentration rises, the parafollicular cells of the thyroid gland increase calcitonin secretion into the blood.
    • The resulting high levels of calcitonin in the blood stimulate the bone to remove calcium from the blood plasma and deposit it as bone.
    • When the blood calcium level is too low, calcitonin secretion is inhibited and PTH secretion is stimulated.
  • Parathyroid Hormone

    • PTH works in concert with another hormone, calcitonin, that is produced by the thyroid to maintain calcium homoeostasis.
    • Parathyroid hormone acts to increase blood calcium levels, while calcitonin acts to decrease blood calcium levels.
    • This interaction between parathyroid hormone and calcitonin is also an important part of bone remodeling.
  • Hormonal Control of Blood Calcium Levels

    • The hormone calcitonin, which is produced by the parafollicular (or C) cells of the thyroid, has the opposite effect on blood calcium levels as PTH.
    • Calcitonin decreases blood calcium levels by inhibiting osteoclasts, stimulating osteoblasts, and stimulating calcium excretion by the kidneys.
    • Calcitonin is most important in children (when it stimulates bone growth), during pregnancy (when it reduces maternal bone loss), and during prolonged starvation (because it reduces bone mass loss).
    • In healthy, nonpregnant, unstarved adults, the role of calcitonin is unclear.
  • Parathyroid Glands

    • PTH opposes the effect of thyrocalcitonin (or calcitonin), a hormone produced by the thyroid gland that regulates calcium levels.
    • PTH and calcitonin work in opposition to one another to maintain homeostatic calcium levels in body fluids.
  • Overview of the Parathyroid Glands

    • PTH has effects antagonistic to those of calcitonin by increasing blood calcium levels by stimulating osteoclasts to break down bone and release calcium.
  • Overview of Endocrine Glands

    • The thyroid also produces and releases the hormone calcitonin (thyrocalcitonin) that contributes to the regulation of blood calcium levels.
    • Thyrocalcitonin or calcitonin decreases the concentration of calcium in the blood, where most of it is stored in the bones.
    • Calcitonin, a hormone produced by the thyroid gland that also regulates ECF calcium levels, serves to counteract the calcium-producing effects of PTH.
  • Overview of the Thyroid Gland

    • The thyroid also produces calcitonin, which plays a role in calcium homeostasis.
  • Paget's Disease

    • Although there is no cure for Paget's disease, medications (bisphosphonates and calcitonin) can help control the disorder and lessen pain and other symptoms.
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