Cells within the human body need to communicate with each other in order to maintain symbiosis of the tissues and organs. This communication is happening not only via the blood stream but also through close cell to cell interaction. As bone forms, cells of different kind gather and release their product towards molecules or other cells acting at the needed sites of remodeling and modeling. The product is a hormonal molecule which influences the behaviour of another cell or its own. In case of bone formation, the hypothalamic-pituitary-thyroid axis and their subsequent release of hormones plays an important role to avoid cessation of growth in children or inadequate bone maturation (6).
In Paracrine signaling, the cell releases its hormone from its cytoplasm into the interstitial gap to act on the neighboring cells provided that they are equipped with the fitting receptor for that special hormone. Following that, the cell reacts to it with a specific answer, which is directly proportional to the timing, concentration and manner of the messenger substance.
Whereas in the Autocrine mechanisms of cell signaling the cell secretes a certain molecule, which was previously synthesized by its own into the interstitial space where it acts at the receptor sites of the same cell. It has to be a pre requisite that this cell is equipped with the matching receptors for the self-secreted molecule (7).