One animal study [19] showed that cigarette smoke inhalation increased serum levels of the hormone calcitoninthe, decreased in lung tissue immunoreactive calcitonin content and caused hypocalcemia. However, another study [20] showed that smokers had lower serum PTH levels than non-smokers, and there was no association between number of cigarettes smoked and serum PTH. The gene discussed is PTH; the disease is Hypocalcemia.