Overview
Calcitonin is a peptide hormone that plays an essential role in maintaining calcium balance in the body. It is produced by the parafollicular cells, also known as C cells, of the thyroid gland. The primary function of calcitonin is to lower calcium levels in the blood when they become elevated. It works as a natural counter-regulatory hormone to parathyroid hormone, helping maintain calcium and phosphate homeostasis.
Calcitonin is released in response to increased blood calcium levels and acts mainly on bones and kidneys. In bones, it inhibits osteoclast activity, reducing bone breakdown and calcium release into the bloodstream. In the kidneys, it decreases calcium and phosphate reabsorption, increasing their excretion in urine. Calcitonin also reduces calcium absorption from the intestines to a smaller extent. Due to its short half-life, its effects are rapid but temporary, allowing fine regulation of calcium levels.
Clinically, calcitonin is an important biochemical marker, particularly in conditions involving thyroid C cells. Its measurement is most valuable in detecting, monitoring, and managing medullary thyroid carcinoma and related disorders.
Symptoms
Abnormal calcitonin levels may be associated with a variety of symptoms, largely related to disturbances in calcium balance or underlying thyroid conditions. Individuals may experience a noticeable lump in the neck due to thyroid enlargement or tumors. Swollen lymph nodes in the cervical region may also be present.
Neuromuscular symptoms can include muscle cramps and tetany, which occur due to altered calcium levels affecting nerve and muscle function. Cardiovascular symptoms such as cardiac arrhythmias, rapid heartbeat, or a pounding sensation in the chest may develop. Some individuals experience dizziness, lightheadedness, fainting, or near-fainting spells. Excessive sweating may also be noted.
These symptoms do not occur in isolation and often indicate an underlying endocrine or thyroid-related condition rather than calcitonin imbalance alone.
Causes
Calcitonin levels can rise or fall depending on various physiological and pathological conditions. High calcitonin levels are most commonly associated with medullary thyroid carcinoma, a tumor originating from thyroid C cells. C-cell hyperplasia, which is a precursor condition, can also lead to elevated levels.
Other causes include certain neuroendocrine tumors such as pheochromocytoma and carcinoid tumors. Chronic renal insufficiency may increase calcitonin due to reduced clearance from the body. Elevated levels may also be seen in pregnancy and newborns as a physiological response.
Low calcitonin levels are usually linked to reduced thyroid C-cell function. This may occur following thyroidectomy, chronic autoimmune thyroiditis, hypocalcemia, or disorders affecting calcium metabolism such as hypoparathyroidism.
Risk Factors
Several factors increase the risk of abnormal calcitonin levels. Individuals with a personal or family history of medullary thyroid carcinoma are at higher risk. Genetic syndromes associated with C-cell disorders increase susceptibility. Chronic kidney disease is another significant risk factor due to impaired hormone clearance.
Smoking and high body weight may contribute to elevated calcitonin levels. Certain medications, including glucocorticoids and beta blockers, can influence calcitonin concentrations. Long-standing thyroid disorders and autoimmune thyroiditis also increase risk.
Regular screening is particularly important in individuals with known thyroid nodules, unexplained neck masses, or a family history of endocrine tumors.
Prevention
While calcitonin abnormalities themselves cannot always be prevented, early detection and risk reduction play a crucial role. Routine thyroid evaluation and monitoring of suspicious thyroid nodules help identify conditions early. Individuals with a family history of medullary thyroid carcinoma should undergo regular screening as advised.
Avoiding smoking and maintaining a healthy body weight may reduce the likelihood of elevated calcitonin levels. Proper management of kidney disease helps prevent hormone accumulation. Monitoring calcium balance and addressing thyroid disorders promptly can reduce complications.
