Endorphins

Hans Walter Kosterlitz 1975, the endorphins were found in the pig's diencephalon. This is the origin of the first name for the endorphin group: "Enkephalins" (from Greek kephalos - head).

Endorphins are endogenous opioid peptides that are produced in the pituitary gland and hypothalamus of vertebrates. They arise from a precursor protein, proopiomelanocortin (POMC). Proopiomelanocortin is produced in the hypothalamus. In the pituitary gland, endorphins (above all beta-endorphin) are split off from it in addition to other substances (ACTH, MSH, lipotropin).

Essentially, 3 types of endorphins are distinguished:

• alpha endorphin
• beta-endorphin (the knowledge about endorphins mainly refers to beta-endorphin)
• gamma endorphin.

Chemically speaking, endorphins are short neuropeptides that bind to opioid receptors. Endorphins have as a common structural feature a peptide group with four amino acids (tetrapeptide) of the sequence tyrosine-glycine-glycine-phenylalanine

Places of formation of endorphins (The following data refer mainly to beta-endorphins) are the hypothalamus and the pituitary gland. These hormones are formed from a precursor protein, proopiomelanocortin (POMC). The POMC is formed in the hypothalamus, from which endorphins (beta-endorphin) are cleaved in the pituitary gland in addition to other substances (ACTH, MSH, lipotropin).

Endorphins are the natural ligands for opioid receptors. Opioid receptors are expressed in the CNS and the peripheral nervous system, but also in many peripheral organs such as the gastrointestinal tract. According to current knowledge, the endogenous opioid system is one of the most important pain-relieving systems in the body. Afferent stimuli are modulated in such a way that they are not transmitted unhindered into the CNS. There is good evidence that beta-endorphin levels could serve as a biomarker for the quantification of pain symptoms (Choi HY et al. 2019).

For example, the endorphin system is activated in emergency situations. It is associated with the production of sex hormones and is held jointly responsible for the development of "feelings of happiness". It is assumed that certain physical exertions and pain experiences cause a feeling of happiness through the release of endorphins. This effect is now medically recognised, although it is experienced in very different ways by different individuals.

Endorphins promote the feeling of hunger and have a positive effect on deep and peaceful sleep. Furthermore, endorphins influence vegetative processes such as body temperature or intestinal mobility. The influence of endorphins on immunological reaction processes is also described (Tishevskaya NV et al. 2017).

The word endorphin is a cross between the words "endogenous and morphine" and refers to the endogenous production of an opioid.

1. Bodnar RJ (2019) Endogenous opioid modulation of food intake and body weight: Implications for opioid influences upon motivation and addiction. Peptides 116:42-62.
2. Choi HY et al (2019) Can Beta-Endorphin Be Used as a Biomarker for Chronic Low Back Pain? A Meta-analysis of Randomized Controlled Trials. Pain Med 20:28-36.
3. Dhaliwal A et al (2019) Physiology, Opioid Receptor. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing, PMID: 31536249.
4. Shenoy SS et al (2019) Biochemistry, Endogenous Opioids. StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing PMID: 30422494
5. Tishevskaya NV et al (2017) Sensitivity of T-Lymphocytes to Hormones of the Anterior Pituitary Gland. Usp Fiziol Nauk 48:80-90.