Hydrophilic Hormones

Peptide hormones are hydrophilic and generally have a very short half-life in the blood - a few minutes to hours, as they are quickly destroyed by peptidases. Thus only a small part of the hormones released reaches the successful organs. The peptide hormones reach the respective target cell as humoral or first messenger substances in an extracellular way. In addition to steroid hormones, thyroid hormones T3 and T4 and D-hormone, the outer side of the cell membrane has hormone receptors for the respective hydrophilic hormone. this hormone-receptor binding - with a few exceptions such as insulin, prolactin, T3, growth hormone - leads to the enzymatic release of second messenger substances or second messenger via certain reaction steps between proteins of the cell membrane.