Calcitonin (thyroid tumor marker)

Why this test? 

For the diagnosis of medullary thyroid cancer. 

To detect the syndrome of multiple endocrine neoplasia (MEN-IIa, Sipple's disease), which can manifest as brain cancer, tumor of the medulla of the adrenal glands (phaeochromocytoma), or hyperplasia of the parathyroid glands and hyperparathyroidism. 

To find out if there are metastases of medullary thyroid cancer. 

For indirect assessment of the size of medullary carcinoma. 

To assess the outcome of surgery to remove medullary thyroid cancer. 

For the diagnosis of primary osteoporosis.

For the diagnosis of hyper- and hypoparathyroidism.

In what cases is it prescribed?

When medullary carcinoma is suspected (with nodular formations of the thyroid gland, an increase in its size, an increase in regional lymph nodes).

When diagnosed with pheochromocytoma, hyperparathyroidism to rule out the syndrome of multiple endocrine neoplasia (MEN IIa). 

Before and after surgery to remove medullary carcinoma.

If one of the patient's relatives had brain cancer. 

With symptoms of osteoporosis (pain in the bones, their deformation and multiple fractures) for a comprehensive assessment of calcium metabolism disorders. 

With disorders of calcium-phosphorus metabolism (with hyper-, hypoparathyroidism)

Testing preparation 

Stop taking oral contraceptives a month before the testing. 

Testing  information 

Calcitonin is a thyroid hormone produced in parafollicular cells (C-cells), one of the most important regulators of calcium-phosphorus metabolism. The formation of calcitonin directly depends on the level of calcium in the blood: when it increases, the concentration of calcitonin increases, and when it falls, it decreases. 

Once in the blood, calcitonin quickly disappears from it, its half-life, according to various sources, is from 2 to 15 minutes. Osteocytes (bone cells) have special receptors, acting on them, calcitonin increases the flow of calcium from the blood into the bones, which inhibits bone resorption (destruction, decrease in mineral density).

Thus, the action of calcitonin is aimed at lowering the level of calcium in the blood, inhibiting bone demineralization. Calcitonin is a direct antagonist of parathyroid hormone (PTH), a hormone of the parathyroid glands. 

The effect of PTH is directly opposite to the effect of thyrocalcitonin, although it is also regulated by the concentration of calcium in the blood. It removes calcium from the bones to maintain its required concentration in the blood. 

Calcitonin and PTH in a healthy person, interacting with each other, are in balanced amounts for the normal regulation of calcium-phosphorus metabolism, which is mainly responsible for bone density. Vitamin D3 plays an important role in regulating the PTH-calcitonin relationship. 

Thus, measuring the level of calcitonin is first of all advisable in case of disturbance of calcium-phosphorus metabolism caused by primary osteoporosis.

It should be remembered that the level of calcitonin must be evaluated in combination with other markers of bone remodeling. 

In secondary osteoporosis (caused by hypercorticism, hypogonadism, thyrotoxicosis, hyperparathyroidism), the level of calcitonin does not decrease. The calcitonin test is extremely important in the diagnosis of medullary thyroid cancer, including the detection of multiple endocrine neoplasia syndrome (MEN-IIa, Sipple disease), which can present as brain cancer, adrenal medulla tumor (phaeochromocytoma), or parathyroid hyperplasia and hyperparathyroidism. 

An increase in the concentration of calcitonin in blood serum during a test with pentagastrin is the main diagnostic criterion for the presence of medullary carcinoma of the thyroid gland, the stage of the disease and the size of the tumor are judged by the results of the study.

After the administration of pentagastrin, the level of calcitonin increases in almost all patients with medullary thyroid cancer. If it was already elevated, it will increase 10-20 times during the test with pentagastrin.

When the calcitonin level is in the lower limits of the normal range or is not detected at all, and after stimulation with pentagastrin it increases significantly, but does not go beyond the normal range, an early stage of medullary cancer or C-cell hyperplasia of the thyroid gland is suspected. In some patients, intravenous administration of calcium preparations should be used as stimulation, as tumors may not respond to pentagastrin. 

Analysis of calcitonin is prescribed after surgical treatment of medullary carcinoma of the thyroid gland to evaluate the results of the operation. In addition, it is recommended to give it in the late postoperative period to monitor whether the medullary carcinoma has metastasized and whether there is a recurrence of the tumor. Since the secretion of calcitonin can be affected by enzymes of the gastrointestinal tract (pepsin), glucagon produced by the pancreas, diseases of these organs (pancreatitis, acute cholecystitis, liver cirrhosis) can indirectly affect the synthesis of calcitonin.