Now, the parathyroid hormone is a peptide hormone and what that basically means is it is produced in the rough endoplasm reticulum of the chief cells and then it is modified in the golgi apparatus. Now, because it's a peptide hormone, that implies it's water soluble and so it is soluble in our blood. And that means we do not require any type of protein carrier to actually transport the parathyroid hormone in our blood system. Now, when the parathyroid hormone actually reaches its target cell, because it is not soluble in lipids, that means it cannot actually pass across the membrane of the target cell. Instead it binds onto the membrane of the target cell, it binds to special protein receptors and initiates a secondary messenger system that basically creates some type of change inside the cell. Now the question is, what exactly is the function, what is the purpose of the parathyroid gland or the parathyroid hormone?