Calcitonin

Calcitonin is a polypeptide hormone consisting of 32 amino acids, which in humans (hCT) is formed in the C-cells ("C" for calcitonin) of the thyroid gland and is released in proportion to the calcium concentration of the blood plasma. It is used as a specific sensitive tumor marker in the diagnosis and monitoring of medullary thyroid carcinoma (C-cell carcinoma).

Calcitonin causes a rapid and short-lasting reduction in calcium and phosphate concentrations. It promotes calcium and phosphate excretion via the intestines and kidneys.

The peptide hormone calcitonin acts functionally as an antagonist to parathyroid hormone(formed in the parathyroid glands).

Calcitonin promotes the excretion of calcium, phosphate and sodium via the intestines and kidneys. The peptide hormone also has an analgesic effect. During human growth, it inhibits osteoclast function; in adulthood, it promotes the incorporation of calcium into the osteoid.

Normal values: Women: up to 5 ng/l. Men: up to 8.4 ng/l.

Calcitonin is used as a tumor marker in medullary thyroid carcinoma.

The normal value in adults is less than 10 ng/l (corresponds to 2.8 pmol/l). Conversion factor from ng/l to pmol/l for calcitonin: ng/l × 0.28 = pmol/l. There is probably no such thing as too low a calcitonin level. Calcitonin can also be below the detection limit of currently available tests in healthy people.

Elevated calcitonin levels are found:

• rarely in hyperthyroidism
• in medullary thyroid carcinoma (C-cell carcinoma)
• in C-cell hyperplasia (e.g. in the context of multiple endocrine neoplasia, type IIa (MEN-IIa)
• renal insufficiency
• in liver cirrhosis
• in neuroendocrine tumors, such as small cell lung carcinoma, carcinoids, insulinomas, VIPomas, hCT can be formed paraneoplastically. hCT can serve as a progression parameter in these cases.

Note: For the differential diagnostic evaluation of hypercalcitoninemia, a stimulation test with pentagastrin (pentagastrin stimulation test) or calcium is indicated (recommendation of the Thyroid Section of the German Society of Endocrinology).

Low calcitonin values:

• However, low values do not play a role in diagnostics.

Calcitonin as medicine

Indication: Osteoporosis; Paget's disease (osteodystrophia deformans). Hypercalcemia syndrome in tumor diseases (dosage: 100IE every 6-8h); preventive use in immobile patients to prevent acute bone mass loss (100 IU/die).

Related to calcitonin is the "Calcitonin Gene-Related Peptide" (CGRP), a neuropeptide with effects in the CNS and peripheral nervous system. CGRP is encoded by the same gene as calcitonin and is produced in the periphery by selective splicing of mRNA (Note: CGRP plays an important pathophysiological role in the pathophysiology of migraine).

1. Hermann PT et al (2014) Hunnius Pharmaceutical Dictionary, 11th edition, De Gruyter Publishers pp. 320-321