Calcitonin
Calcitonin is a hormone the thyroid makes and releases to help regulate the level of calcium in the blood by decreasing it. The C-cells in the thyroid, also called parafollicular cells, make and secrete it. Calcitonin opposes the actions of parathyroid hormone, which increases blood calcium levels. It lowers blood calcium in two main ways: it blocks the activity of osteoclasts, the cells that break down bone and release calcium into the bloodstream, and it decreases the amount of calcium the kidneys reabsorb and release back into the bloodstream. Calcitonin is an unusual hormone in that scientists know what it does but do not fully understand why we have it.
Why it matters: Abnormal calcitonin levels cause few or no symptoms, so a calcitonin blood test is typically ordered only in particular circumstances: to help diagnose medullary thyroid cancer or C-cell hyperplasia, to monitor the treatment of medullary thyroid cancer, or where there is a family history of multiple endocrine neoplasia type 2. Parathyroid hormone appears to have a more important role in regulating blood calcium than calcitonin does, and an abnormal calcitonin level does not have much effect on the body.
Source · Cleveland Clinic — what it is, why it matters, what moves it, related conditions
May increase with:
May decrease with:
What is Calcitonin?
Calcitonin is a hormone the thyroid makes and releases to help regulate the level of calcium in the blood by decreasing it. The C-cells in the thyroid, also called parafollicular cells, make and secrete it. Calcitonin opposes the actions of parathyroid hormone, which increases blood calcium levels. It lowers blood calcium in two main ways: it blocks the activity of osteoclasts, the cells that break down bone and release calcium into the bloodstream, and it decreases the amount of calcium the kidneys reabsorb and release back into the bloodstream. Calcitonin is an unusual hormone in that scientists know what it does but do not fully understand why we have it.
What might a high or low Calcitonin mean?
Abnormal calcitonin levels cause few or no symptoms, so a calcitonin blood test is typically ordered only in particular circumstances: to help diagnose medullary thyroid cancer or C-cell hyperplasia, to monitor the treatment of medullary thyroid cancer, or where there is a family history of multiple endocrine neoplasia type 2. Parathyroid hormone appears to have a more important role in regulating blood calcium than calcitonin does, and an abnormal calcitonin level does not have much effect on the body.
What is the typical reference range for Calcitonin?
The general-population reference range shown here is < 8.4 pg/mL. Reference ranges describe the general population and are not a personal target — discuss your results with your physician.
What can affect Calcitonin?
It may be higher with: Rising blood calcium — when blood calcium levels increase, the thyroid releases calcitonin in higher quantities, Medullary thyroid cancer, a rare cancer beginning in the C-cells, which can cause those cells to make excess amounts of calcitonin, C-cell hyperplasia, a benign condition of abnormal C-cell growth whose enlarged tissue can release excess calcitonin. It may be lower with: Falling blood calcium — when blood calcium levels decrease, the thyroid decreases the amount of calcitonin it releases, Removal of the thyroid, after which calcitonin can be undetectable.
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