Inthira ChaiyaChontita RattanakulSahattaya RattanamongkonkulWannapa PanitsupakamonSittipong RuktamatakulMahidol University2018-10-192018-10-192013-11-04International Journal of Mathematics and Computers in Simulation. Vol.7, No.5 (2013), 398-405199801592-s2.0-84886709352https://repository.li.mahidol.ac.th/handle/20.500.14594/31609Calcium is essential for human. Apart from providing skeletal strength, calcium also plays important role in a wide range of biological functions. In this paper, calcium homeostasis, the mechanism that maintains the serum calcium level to be in the normal range, is investigated mathematically. A mathematical model is formulated to incorporate the effects of parathyroid hormone, vitamin D and time delay on calcium homeostasis. The conditions on the model parameters for which a periodic solution exists are then derived by means of Hopf bifurcation theorem. Moreover, various kinds of dynamic behavior of the model are also investigated numerically.Mahidol UniversityComputer ScienceMathematicsArticleSCOPUS