During the last decades, drug abuse has been a serious challenge for the public health 1.
Over several centuries opioids were used as painkillers specifically sever pain in serious cancer. The analgesic attributes of opioids have rescued the so many people from suffering and aided them in dealing with acute pain and cancer. Since 1990s the opioid consume has increased in an alarming way 2. Iran has a high rate of opioid consumption following centuries of opioid abuse.
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The use of opioids influences the quality of life by creating a financial burden on the society. This burden is a result of legal actions, unemployment and several their factors 3-6. Long-term opioid use is related to some adverse outcomes other adverse effects and toxicities such as addiction, hypogonadism, immune suppression, osteoporosis and hyperalgesia 7. The other side effects of opioid abuse are as follows: sexual malfunction, reducing libido and infertility, osteoporosis and osteopenia 8. Therefore, numerous studies done on addiction considered the changes caused by this substance in the body 9. It is believed that opioids influence testosterone release through the hypothalamic-pituitary axis and inhibition of Luteinizing hormone (LH) secretion 10, 11. Opioids may decrease gonadotropins both by amending the sex hormone-hypothalamic feedback process and by interfering with the pituitary release of gonadotropins 12. The actions of internal opioid peptides or opioid receptors (OR) are the central issue of some researchers with the aim of explaining neurotransmission and addiction.
Opioid receptors, are peptides that in terms of structural to be consisted of a core domain of 7 transmembrane (TM7) in form ? -helices and a neighbor of peripheral helix 8 (IL4), that related to 3 extracellular (EL1, EL2, EL3) and 3 intracellular (IL1, IL2, IL3) loops, and so contain glycosylated in N-terminal and palmitoylated in C-terminal domains of altered receptors. These show high sequences in their TM domain by 73%-76% and at ILs in 63%-66% and large divergence in N- and C-terminal domains and ELs with 34%-40% identity. The opioid analgesia starts by binding to an opioid agonist to one or more opioid receptor proteins. There are three subtypes of OR have been identified; µ (mu, MOR), ? (kappa, KOR), and ? (delta, DOR) 13,14.
Receptor for natural and synthetic opioids including morphine, heroin, DAMGO (D-Ala, N-MePhe, Gly-ol-enkephalin), fentanyl, etorphine, buprenorphine and methadone 15-19. G-protein coupled receptor (GPCR) which are the receptors for endogenous enkephalins and for a subset of other opioids. Lately, it is known that chronic abuse of opioids causes endocrine dysfunctions in humans.
The most common endocrine dysfunction is hypogonadism resulting in the decreased sexual activity in addition to physical and psychological problems such as fatigue, muscle weakness, osteoporosis, and emotional disturbances 20-22. Further, in a limited cases adrenal insufficiency and adult growth hormone deficiency are reported 23, 24. These endocrine dysfunctions affect the quality of life and result in metabolic abnormalities or other life-threatening conditions such as adrenal crisis 23. Furthermore, these side effects can be prevented stopping or reducing opioid treatment or hormone replacement treatment. However, the opioid-induced endocrine dysfunctions are not widely known 20, 21. Some researcher has been reporting a change in serum trace element contents in drug-addicted individuals and the different levels of these elements in the blood of addicted people in comparison with healthy people were shown 25. The aim of this study is the investigation of testosterone, prolactin, LH, and zinc level in opioids users. The present study is going to investigate the link between these clinical deficiencies and molecular levels and how it is vital to fully understand the opioid pharmaceutical aspects.
Additionally, this will support to better understand and the role of opioid receptors is essential for regulation of different pathophysiological activities.