Tissue hormones, unlike other hormones, are not produced in special glands but in close proximity to their sites of action. They perform a variety of tasks in the body. Some tissue hormones act only on the cells in which they are produced (cell hormones).
What are tissue hormones?
Tissue hormones are also called local hormones. They perform their function in close proximity to their site of formation by acting directly on neighboring cells (paracrine tissue). They overcome the interstitial space filled with blood vessels, nerve fibers and connective tissue and reach the receptors of the targeted cells via these. The bloodstream is not needed as a transport route. There are also local hormones that exclusively affect endocrine tissue. Examples of tissue hormones are prostaglandins (PG), serotonin, histamine, bradykinin and hormones regulating the gastrointestinal tract (substance P). If the tissue hormone acts directly on the cells in which it is produced, it is called a cell hormone.
Function, action, and tasks
Tissue hormones use the principle of diffusion to spread to surrounding paracrine or endocrine tissues. Locally acting hormones influence metabolic processes and regulate body growth and sexual maturation. They are permanently controlled by the central nervous system and higher-level hormones. For example, they are released by a stimulus in the central nervous system. They are also released to maintain hormonal balance (regulatory cycle). Prostaglandins (PG) belong to the group of eicosanoids. As pain mediators, they transmit the sensation of pain, and in the stomach they are involved in building up the mucous membrane that protects the stomach. In vascular inflammation, they prevent platelets from clumping together and therefore also the occurrence of thromboses and embolisms. They dilate blood vessels and contract muscles. In glaucoma, they lower intraocular pressure. The prostaglandin groups E1 and E3 prevent undesirable effects of prostaglandin E2, such as the development of fever. The tissue hormone serotonin acts on the 5 HT receptors. It is mainly active from the intestinal mucosa and influences memory performance and mental well-being. As a “happiness hormone” it provides good mood and better coping with stress. It reduces the feeling of hunger and regulates body temperature. Histamine, which also functions as a neurotransmitter, is released during inflammatory reactions. By stimulating the H2 receptors, it stimulates the formation of gastric juice. In inflammation, histamine release causes tissue swelling at the target site and dilation of blood vessels – actions intended to support the immune response at the affected site. In addition, a strong histamine release causes the appearance of allergic symptoms such as runny nose, watery eyes and skin rash. Via the central nervous system, histamine causes the release of other neurotransmitters.
Formation, occurrence, properties, and optimal levels
Tissue hormones are formed in specialized single cells and, unlike glandular hormones, may be distributed over large tissue regions. Prostaglandins were first discovered in the secretions of the male prostate (hence the name). They are particularly abundant in male sperm, but are also found in many organs. Prostaglandins are produced from the fatty acids gamma-linolenic acid, eicosapentaenoic acid and arachidonic acid – unsaturated fatty acids consisting of 20 carbon atoms and a closed 5-carbon ring. There are prostaglandin groups D2, E1, E2, E3 etc. Histamine is made from histidine. Also, the body makes it from certain foods such as cheese, yeast, and chocolate. It is found almost everywhere (skin, lungs, hypothalamus, gastrointestinal tract) and in increased amounts especially in mast cells, gastric mucosal cells and basophilic granulocytes. About 95% of serotonin is produced in the gastrointestinal tract and also serves as a nerve messenger (neurotransmitter). L-tryptophan is required for its production in the brain, since the body cannot produce serotonin itself. Tryptophan is found in high concentrations in certain foods (nuts, soybeans, mushrooms, sunflower seeds), but must first pass through the blood-brain barrier. Sport facilitates the passage of L-tryptophan into the brain and thus increases serotonin production and release.
Diseases and disorders
Artificially produced prostaglandins dilate peripheral arteries in patients with peripheral arterial disease (pAVD) in stages III and IV. In doing so, they mimic the action of the natural prostaglandin E1. They are also used to heal and prevent ulcers and gastrointestinal inflammation. As an E2 analogue, they serve to induce artificial labor and prevent atonic uterine bleeding. In prostaglandin deficiency, the E1 and E3 groups are insufficiently produced. They normally inhibit the adverse effects of the E2 group. As a result, allergic reactions occur. Serotonin deficiency leads to depressive moods, bad temper, irritability, increased anxiety and migraine. It comes from a deficiency of vitamin B6 and magnesium and is treated with antidepressants that act directly on the brain. In addition, the consumption of coffee, meat and dairy products unfavorably affects the formation of serotonin. In contrast, consumption of L-tryptophan-containing foods such as bananas, nuts, amaranth, mushrooms and chocolate boosts serotonin production. In histamine intolerance, the body’s ability to break down the tissue hormone histamine is impaired. The DAO enzyme required for this only functions insufficiently. This leads to an excess of histamine and to inflammatory and allergic reactions. The patient reacts to the consumption of chocolate, sulfurized dried fruits, cheese and red wine with skin rash, headache, diarrhea, nausea, runny nose and swollen eyes. Sometimes there are even long-term consequences (migraine, eczema). Histamine intolerance is often caused by antibiotics, which have an unfavorable effect on the intestinal bacteria. It also occurs due to vital substance deficiency.
