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The calcitonin hormone, also known as thyrocalcitonin, is synthesized by the c cells of our thyroid gland.
- High levels of calcitonin may be an alarming sign for diagnosing a rare kind of medullary thyroid cancer.
- When it is present at normal levels, it helps control the calcium and potassium levels in our body.
- The secretion of this hormone completely depends upon the blood's calcium levels.
- When calcium levels start increasing, the body secretes calcitonin in response to rising calcium and potassium levels, and as the calcium level begins to drop, so do the calcitonin levels.
- Calcitonin is constituted by a single alpha-helix chain of 32 amino acids and is a peptide hormone secreted by the thyroid gland.
- Apart from lowering calcium and potassium levels in the blood, calcitonin stimulates bond formation as well.
- The molecular formula of calcitonin is C15H226N40O45S3. The molecular weight of calcitonin is 3417.9.
Key Terms: Bone, Calcitonin, Parathyroid, Vitamin D, Secretion, Hormone, Calcium, Potassium, Vitamins, Nutrients
What Is Calcitonin?
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Calcitonin hormone regulates calcium and potassium levels in our body. Calcitonin does not regulate the calcium of bones therefore it focuses only on calcium levels in the bloodstream. Irregularities and abnormalities in calcitonin levels have few or no effects on the body.
- The parathyroid hormone helps in maintaining the correct balance of calcium in the bloodstream. whereas calcitonin decreases calcium levels.
- Thyroid is a part of our endocrine system and it is responsible for the secretion or production of various hormones.
- Calcitonin is a hypocalcemic hormone that decreases Ca+2 ion level in blood.
- Calcitonin-containing other cells are parathyroid, thymus and medullary carcinoma. Synthesis and secretion of calcitonin regulated by plasma Ca+2 concentration.
- As soon as plasma has high Ca+2 concentration then calcitonin is secreted.
- As plasma Ca+2 increases, calcitonin increases, and as there's a decrease of Ca+2 in plasma then calcitonin decreases as well.
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How Does Calcitonin Work?
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Working of calcitonin is explained in the below-mentioned points:
A) Calcitonin inhibits bone resorption ( absorption of bone's calcium in blood) by
- Inhibiting osteoclast activity.
Osteoclast activity is when bone's calcium starts moving in the bloodstream, and this activity needs to be inhibited.
- Inhibit calcium resorption in kidney as well
- Calcitonin inhibits PCT reabsorption of calcium and phosphates.
B) Action of calcitonin is done through,
The action of calcitonin is mediated through G protein-coupled calcitonin receptors.
For mediation of calcitonin, it needs to bind to a receptor so that complex formation can happen which is the reason for its biological activity coming into action.
Calcium Regulation
Measurement of Calcitonin Levels
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Calcitonin levels are measured via a blood test. Blood sample is taken and further checked for diagnosis of MTC (medullary thyroid cancer) or hyperplasia, other than that calcitonin level's abnormalities are nothing to be worried of.
Calcitonin level test is done only for
- Diagnosing medullary thyroid cancer or C-cell hyperplasia
- If somebody has a past history of the condition of endocrine neoplasia type 2.
Normal ranges for calcitonin are:
- For males: 0 to 7.5 pg/mL
- For females: 0 to 5.1 pg/mL
Calcitonin Uses
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Some uses of Calcitonin include:
- Calcitonin can be used as a medicinal drug.
- Whenever there's a condition of Hypercalcemic state or hyper parathyroid.
- Used for curing Postmenopausal Osteoporosis.
- Used as a nasal spray.
- Paget's disease (bisphosphonates are preferred and then calcitonin is used).
- Diagnosis of medullary carcinoma of thyroid.
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Importance of Calcitonin
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Our bones and body need calcium, and it helps to:
- Build and maintain strong bones
- Regulates muscle contraction
- Balanced pH levels
- Transportation of nutrients
However, when the calcium level in the blood rises above normal then this condition is commonly known as Hypercalcemia.
What is Calcitonin Inforgraph?
Discovery of Calcitonin
Calcitonin was discovered by Douglas Chopp and Bcheney at the University of British Columbia, Canada. In the beginning, this hormone was considered to be secreted by the parathyroid gland.
Later Lain Macintyre and team at royal postgraduate medical school located in London concluded that calcitonin was discovered by the parafollicular thyroid gland. Dr. Chopp found this hormone because of its responsibility of maintaining normal calcium tone.
Things to Remember
- Calcitonin hormone regulates calcium and potassium levels in our body.
- Calcitonin does not regulate the calcium of bones therefore it focuses only on calcium levels in the bloodstream.
- Calcitonin containing other cells are parathyroid, thymus, and medullary carcinoma.
- Synthesis and secretion of calcitonin regulated by plasma Ca+2 concentration
- As soon as plasma has a high Ca+2 concentration then calcitonin is secreted. Thus, as plasma Ca+2 increases, calcitonin increases.
Read More:
Previous Year Questions
- Who is known as ''father of endocrinology''...[BHU UET 2006]
- Hyposecretion of growth hormone causes:...[BCECE 2004]
- Which of the following is not true for hormones...[GUJCET 2009]
- Hypersecretion of mineralocorticoids leads to...[BHU UET 2009]
- FSH is secreted by..[BHU UET 2005]
- Which hormone promotes cell division, protein synthesis...[BHU UET 2008]
- It helps in differentiation of cells of the immune system...[GUJCET 2008]
- With increasing age, secretion of which of the following reduces...[GUJCET 2007]
Sample Questions
Ques. Both Parathyroid and calcitonin work the same? (3 marks)
Answer. Parathyroid and calcitonin basically have the same motive, as both of them help in regulation of levels of calcium in our bloodstream.
- It is really important as excessive calcium can disrupt not only bone health but also our brain and heart's functioning.
- The only difference is how they affect those calcium levels, PTH controls the calcium levels by increasing their levels and maintaining them to a healthy level, it also controls vitamin D and phosphorus in blood whereas calcitonin maintains the calcium levels by decreasing them.
Ques. What is the Function of calcitonin? (1 mark)
Answer. Calcitonin aims at controlling and decreasing the high calcium levels present in the bloodstream (and not in bones).
Calcitonin blocks the osteoclasts ( who are responsible for breaking bone and releasing calcium from bone to bloodstream) and calcitonin can also decrease the level of calcium reabsorbed by our kidneys and then it is further released back to the bloodstream.
Ques. What is the effect of calcitonin on bone? (1 mark)
Answer. Calcitonin doesn't affect bone. It focuses on maintaining calcium levels in the bloodstream only, and it secretes only when the calcium level of the bloodstream rises.
Calcitonin works for decreasing the high calcium levels in the bloodstream and it blocks or inhibits the osteoclasts which are the cells responsible for the breaking of a bone.
Ques. Differentiate osteoclasts and osteoblasts? (2 marks)
Answer. Osteoblast is basically a bone-forming cell which works for the formation of bones. Initially, it helps in bone formation and later helps to remodel it.
Osteoblasts are made from osteogenic cells in the periosteum whereas osteoclasts are a type of bone cell which are responsible for bone resorption and are involved in bone breakdown, osteoclasts are present on the bone's surface.
Osteoclasts are made from monocytes or macrophages.
Ques. What are the symptoms that may suggest you take a calcitonin test, and are there any precautions to take before the test? (3 marks)
Answer. Some of the symptoms that might suggest you go for a calcitonin test are:
- A lump in the front of your neck
- Swollen lymph nodes in your neck
- Pain in your throat and/or neck
- Trouble swallowing
- Change to your voice, such as hoarseness
Ques. What is the molecular weight of calcitonin and is there any synthetic version of it? (2 marks)
Answer. Calcitonin's molecular formula is C145H240N44O48S2 and upon calculation of molecular weight of respective atoms (C= 12 ,H=1 , N=14 , O= 16 ,S= 32.) Calcitonin acetate ( derived from salmon) is the synthetic version of calcitonin and it's a polypeptide of 32 amino acids, the same as just the original.
Ques. What is the amino acid sequence of calcitonin acetate (salmon)? (2 marks)
Answer. Amino acid sequence of calcitonin acetate (salmon) is:
Cys-Ser-Asn-Leu-Ser-Thr-Cys-Val-Leu-Gly-Lys-Leu-Ser-Gln-Glu-Leu-His-Lys-Leu-Gln-Thr-Tyr-Pro-Arg-Thr-Asn-Thr-Gly-Ser-Gly-Thr-Pro-NH2.
Ques. Why is osteoclast blocked by calcitonin ? (2 marks)
Answer. Calcitonin blocks osteoclasts. Osteoclasts are the cells responsible for breaking down the bond and once the bones are broken calcium from that bone is then sent to the blood. This inhibition of osteoclasts decreases the amount of calcium that is released into the bloodstream.
Ques. Who discovered calcitonin and how did this belief change? (4 marks)
Answer. Calcitonin was discovered by Douglas Chopp and Bcheney at the University of British Columbia, Canada. In the beginning, this hormone was considered to be secreted by the parathyroid gland.
Later Lain Macintyre and team at royal postgraduate medical school located in London concluded that calcitonin was discovered by the parafollicular thyroid gland. Dr. Chopp found this hormone because of its responsibility of maintaining normal calcium tone.
Ques. State the importance of Calcitonin. (3 marks)
Answer. Our bones and body need calcium, and it helps to:
- Build and maintain strong bones
- Regulates muscle contraction
- Balanced pH levels
- Transportation of nutrients
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