Calcitonin hormone and calcium levels


in our endocrine system, thyroid gland has a big role. It secretes and moderates various hormones and Calcitonin is one of them. the hormone was first named thyrocalcitonin since it is produced by thyroid glands(not parathyroid glands).
before we dive deeper into calcitonin itself, first let’s talk a little about bones first:
osteoclasts and  Osteoblasts are the two main cells participating in the process of bone remodelling.

Osteoclasts are responsible for degenerated bone resorption and osteoblasts are responsible for new bone formation.
Bone remodeling is the continuing process of synthesis and degeneration of bones that makes their structure more mature and aids in maintaining normal calcium levels in our body.
also keep in mind Gastrin is a hormone that stimulates the stomach to release gastric acid which allows the stomach to break down proteins taken from food and absorb certain vitamins and minerals.

If your blood work indicates high or low calcitonin levels, ask your doctor whether the underlying cause or issue is with your thyroid. Specifically, if your levels are high, consider asking why or requesting further testing to rule out cancer. high or low calcitonin levels have little affect on your overall health. Still, if you have concerns, talk to an endocrinologist to ensure you are getting support from a hormone specialist.


what is Calcitonin?

Calcitonin(CT) is a (32 amino acid polypeptide) hormone that the C-cells(parafollicular or calcitonin cells) in the thyroid gland produce and release. CT is primarily metabolized by the kidney.
When the level of serum calcium is raised(due to parafollicular cells present in the thyroid gland), it results in the production of calcitonin.
Salmon CT, which differs from human CT in 16 amino acids, has been used for treatment of hypercalcemia.
Gender and age differences have been shown with women having lower CT values than men and with decreasing CT values with age in some, but some studies have been showing otherwise as well so we cannot know for sure.

Because Calcitonin is stimulated by gastrointestinal hormones such as gastrin, interest developed in the concept that CT secretion after eating acted to facilitate calcium deposition in bone and promote bone mass, However, in studies in children with congenital hypothyroidism and in thyroidectomized patients, bone loss has been attributed to inadequate thyroid replacement and not to the absence of CT.

It has been suggested that CT uses phosphate to store calcium in bone after eating But except perhaps for pregnancy and lactation, no specific CT deficiency or excess bone syndromes have been identified. CT has been used to treat osteoporosis(especially in post-menopausal).
high calcitonin levels may be due to Intestinal, gastricbronchial carcinoids, Chronic renal failure, Zollinger-Ellison syndrome, pernicious anaemia and Cancer of the lung, breast, or pancreas. also Pregnant females at term and Newborns might suffer from high calcitonin as well.
Calcitonin gene-related peptides and several other peptides such as intermedin, amylin, and adrenomedullin are categorized in calcitonin family.


How does calcitonin work?

When the osteoclasts break down bone tissue, the calcium enters the bloodstream. By preventing the breakdown of bone, calcitonin lessens the amount of calcium in the blood. The hormone also seems to decrease the amount of calcium the kidneys can re-absorb, lowering levels further.
Secretion of this hormone is controlled directly by the blood’s calcium levels. When the levels start to increase, the body responds with increased calcitonin levels. When calcium levels drop, so do calcitonin levels.


parathyroid hormone vs calcitonin?

calcitonin counteracts parathyroid hormone(PTH) in order to help regulate both blood’s calcium level and blood’s phosphate level. Parathyroid hormone increases blood calcium levels, while calcitonin decreases blood calcium levels. This interaction between these two is crucial for bone remodeling. calcitonin hormone decreases osteoclasts activity which protects against the development of hypercalcemia, a condition in which the calcium level in your blood is above normal range.parathyroid hormone increases osteoclasts activity which protects against the development of hypocalcemia, a condition in which the calcium level in your blood is below normal range.

CT is an older hormone phylogenetically than PTH dating back to fish in the ocean with a need to protect against hypercalcemia while PTH developed in land-dwelling animals to protect against hypocalcemia. As such, this may be an explanation why salmon CT is more potent than CT from mammals.
in comparison to parathyroid hormone, the role of calcitonin in the regulation of serum calcium in humans is minor.

The adapting of PTH and CT secretion to the existing serum calcium concentration is an interesting phenomenon that may reflect a broader concept of physiologic adaptation. For example, adaptation to cold and hot weather as well as oxygen adaptation to high altitude in Himalayan mountain climbers is well known. However, adaptation of hormonal effects and secretion is less well appreciated. In type 1 diabetic patients, an unawareness of hypoglycemia is associated with prolonged insulin therapy and frequent episodes of hypoglycemia.

In a study of patients before and after removal of insulinomas (baseline serum glucose, 50 ± 7 mg/dL), symptomatology as well as the epinephrine, norepinephrine, glucagon, growth hormone, and cortisol response to a hypoglycemic clamp was greatly blunted. After resection of the insulinoma, these same responses became similar to those in normal subjects.

What can go wrong with calcitonin?

patients who have had their thyroids removed will have virtually no calcitonin levels, but they show no resulting symptoms. While doctors know what it does, they do not understand why we have it, and few symptoms occur if levels are high or low. The body appears to function normally, even with high or low levels of this thyroid hormone
Sometimes high calcitonin levels can point to a rare type of medullary thyroid cancer but it is not the calcitonin levels itself that cause the cancer.