Calcitonin
Calcitonin is a thyroid hormone which primary role is to regulate calcium (Ca) metabolism. The purpose of calcitonin is, firstly, to lower blood levels of calcium, as high concentrations of this trace element (hypercalcemia) are harmful to the body, through its increased excretion in the urine and absorption by bone tissue. Secondly, the purpose of calcium is the retention of calcium in the bones during periods of increased calcium loss (pregnancy and breastfeeding). In other words, when calcium levels rise, calcitonin levels rise, and vice versa. Calcitonin functions in close conjunction with parathyroid hormone called parathormone, and is its antagonist.
Calcitonin functions are:
- Slowing down the absorption of calcium in the intestine
- Increased excretion of calcium and phosphorus in the urine, due to impaired reabsorption by the kidneys
- Increased activity of the cells (osteoblasts) which build new bone tissue
- Slowing down the activity of cells (osteoclasts) which destroy bone tissue.
The primary purpose of calcitonin as a laboratory index is to screen for medullary thyroid cancer. Medullary cancer is a tumor of cells which produce osteocalcin. Consequently, when this pathology occurs, there is an increased production of the hormone. This type of cancer is the third most common among all types of thyroid tumors.
Symptoms of medullary thyroid cancer include:
- Diarrhea.
- Sudden attacks of blood rush to the face
- Thyroid gland enlargement
- Difficult swallowing
- Pain in the neck area
- Voice changes, hoarseness
- Cough unrelated to cold
In general, the disease has a relatively favorable prognosis if detected early. Thus, according to the American Cancer Society, when treating cancer of stage, I, the five-year survival prognosis is 99%, stage II - 98%, stage III - 81%, and stage IV - 28%. It is worth noting that in 25% of cases the disease is familial in nature (connected with a mutation of the proto-oncogene), thus, detection of medullar cancer in a patient requires evaluation of all family members. After treatment, lifelong monitoring is necessary for early prevention of disease recurrence: every 4 months for the first 3 years, and every 6 months thereafter.
Calcitonin determination for the purpose to diagnose thyroid cancer is of a screening nature, i.e., it is recognized as the best way to detect pathology early. However, a high calcitonin level alone is not a reason to make a “cancer” diagnosis, but only indicates the need for more thorough, detailed, and expensive examination to confirm or rule out the diagnosis. If there are clinical signs of the disease, but the calcitonin level is within normal limits, then the pentagastrin analysis or provocation analysis is resorted to by intravenous calcium drugs, which “provokes” the tumor to a massive release of calcitonin into the bloodstream. There are no adverse health consequences of this diagnostic procedure, but it is highly informative, as there is a 10-20-fold increase in calcitonin concentrations.
The hormone is also informative in primary osteoporosis which can be postmenopausal, senile and idiopathic as a decrease in calcitonin levels leads to calcium uptake by bone tissue and a decrease in bone mineral density. In this case it is recommended to determine other osteoporosis markers as well: osteocalcin and Beta Cross Laps.
Attention! The analysis may require special preparation: pentagastrin analysis or provocative analysis by administering calcium preparations, therefore it is recommended to consult your attending physician.