Changes of parathyroid hormone in the serum of fluorosis rats taking different levels of calcium

Objective To dynamically investigate the effect of fluoride on the parathyroid hormone in the serum of rats with different calcium intake. Methods 3×2×3 factorial design were used and SD rats were taken as the experimental objects. Rats with different weights were randomly allocated into 6 groups: low calcium control group, low calcium and excessive fluoride group, normal calcium control group, normal calcium and excessive fluoride group, high calcium control group and high calcium and excessive fluoride group. One third of rats were killed ever eight weeks, dental fluorosis of rats were examined, fluorine in the serum and bones of rats, and the levels of calcium and parathyroid hormone in the serum of rats were determined. Results Rats taking excessive fluoride with different calcium intake were all suffered fluorosis. Constantly taking excessive fluoride, fluorosis rats had an increasing tendency of the level of parathyroid hormone in their serum, but only those taking low or high calcium and excessive fluoride had significant difference compared with those taking normal calcium (P 0.01 or 0.05). At the early phase of the experiment, the levels of serum calcium decreased in the fluorosis rats with normal and high calcium intake(P 0.01), later only in the fluorosis rats with high calcium intake(P 0.05). Conclusions Taking excessive fluoride for a long time leads to a compensative increase level of parathyroid hormone in the serum of rats, to maintain the serum calcium concentration in a normal range, which is important for living things to survive. High calcium intake can decrease the accumulation of fluorine in the fluorosis body.