Calcitonin - Functions, Uses, Significance, and Calcitriol

Calcitonin: Calcitonin is secreted by the parafollicular cells within the thyroid gland. Calcitonin is a peptide hormone. It originates from the thyroid gland's parafollicular cells. Its discovery in 1961 marked a milestone in understanding calcium regulation. Calcitonin counters high blood calcium levels. Its primary role involves inhibiting osteoclast activity facilitate calcium deposition in bones and preventing hypercalcemia.

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What is Calcitonin?

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Calcitonin Function

1. Inhibits osteoclast activity : Calcitonin works by suppressing the activity of osteoclasts, cells responsible for breaking down bone tissue. This inhibition prevents the excessive release of calcium from bones into the bloodstream.
2. Promotes calcium deposition in bones : Calcitonin encourages calcium deposition into bone tissue by inhibiting osteoclasts, which helps maintain bone density and strength.
3. Reduces calcium reabsorption in the kidneys : Calcitonin decreases calcium reabsorption and limits the amount of calcium returned to the bloodstream.
4. Increases calcium excretion in urine : By reducing calcium reabsorption, calcitonin facilitates the excretion of excess calcium in the urine and aids in eliminating surplus calcium from the body.
5. Regulates blood calcium levels : Through its actions on bone and kidney function, calcitonin helps to regulate the concentration of calcium in the bloodstream and ensures it remains within the normal range.
6. Acts in opposition to parathyroid hormone (PTH) : While PTH increases blood calcium levels by stimulating bone resorption and enhancing calcium reabsorption in the kidneys, calcitonin works counteractively to lower blood calcium levels, thereby maintaining balance in calcium regulation.

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Uses of Calcitonin

1. Treating High Blood Calcium and Osteoporosis : Calcitonin lowers high blood calcium levels and manages osteoporosis. It is a condition characterized by weakened bones. Injecting calcitonin under the skin has been effective in reducing fractures and preserving bone density, especially in women with type 2 diabetes.
2. Potential Treatment for Bipolar Disorder : Research suggests that injecting calcitonin under the skin may help manage bipolar disorder. Studies show significant reductions in symptoms like irritability, euphoria, and hyperactivity in patients with mania. However, more research is needed to confirm its effectiveness.
3. Identifying Medullary Thyroid Cancer (MTC) : High calcitonin levels can indicate MTC, a rare type of thyroid cancer. Monitoring calcitonin levels before and after surgery helps detect cancer recurrence. Biopsies from suspicious lesions, like swollen lymph nodes, can also be tested for calcitonin to confirm metastases from MTC.
4. Setting Diagnostic Cutoffs : Specific calcitonin levels are suggested to distinguish MTC cases. Higher values raise suspicion of the disease. These cutoffs vary by gender and age, with different thresholds for females, males, and children of varying age groups.

Clinical Significance of Calcitonin

1. Diagnostic Marker for Diseases : Calcitonin is a biomarker for thyroid disorders and bone diseases. The high calcitonin levels can indicate conditions like medullary thyroid carcinoma (MTC) and aid in diagnosis and monitoring.
2. Therapeutic Applications : Calcitonin is utilized therapeutically in treating hypercalcemia and osteoporosis. It helps regulate blood calcium levels and promotes bone health by inhibiting bone breakdown.
3. Potential Research and Development : Ongoing research studies novel applications of calcitonin, including its potential in managing psychiatric disorders. Studies aim to understand its interactions with other hormones and signaling pathways for improved therapeutic strategies.

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