The thyroid is a little gland in the throat that resembles a butterfly greatly. Special thyroid cells create the hormone calcitonin. The thyroid is primarily responsible for producing a number of hormones that serve a variety of functions in the human body. The presence of calciumtonin controls blood calcium levels and reduces calcium reabsorption by the kidneys. Thyroid carcinoma is one of the main conditions caused by calcitonin. C-cell hyperplasia and medullary thyroid carcinoma are two disorders that develop when too much calcitonin is generated. Thyroid disorders begin with C-cel hyperplasia, which may or may not progress to medullar thyroid cancer.