Opioid Effects on Endocrine Function

Opioid Effects on Endocrine Function

Opioids, also known as analgesics or "pain relievers", have undergone much research and have been conclusively linked to dysfunctions and negative interactions within the Endocrine system. The Endocrine System plays a vital role in everyday functions and processes necessary for life and is primarily a communicative system. This system works with the nervous system and together they coordinate bodily functions; however, the endocrine system uses hormones travelling through the blood stream rather than neurotransmitters released from neurons in the nervous system. The pituitary, thyroid, parathyroid, pineal, and adrenal glands as well as the gonads, hypothalamus, pancreas, and heart are some of the main organs associated with the endocrine system, therefore meaning that these organs are directly affected by any type of disruptors associated with the endocrine system.

Throughout the 1990's, research about nonmalignant, chronic pain was commanding national attention and the increasing public awareness also made the problem of high interest to consumers resulting in an increase in the sales of opioid medications. Some of the most commonly recognized opioid drugs include: hydrocodone, oxycodone, and morphine which are often used to alleviate severe pain while codeine is an opioid used for milder pain. Opioids act by attaching to specific proteins called opioid receptors, which are found in the brain, spinal cord, and gastrointestinal tract. When these opioid compounds attach to certain opioid receptors in the brain and spinal cord, the way a person experiences pain can be effectively altered alleviating that pain. Short-acting opioids (SAO) have a relatively quick onset of action and a short duration of analgesic activity while long-acting opioids (LAO) are most of the time opposite with a longer onset of action along with a longer duration of analgesic activity; however, both types of opioids can have devastating adverse effects on the endocrine system ranging from depression and fatigue to sexual dysfunction.

Sex-hormone deficiency, also known as central hypogonadism, results from the attachment of opioids to opioid receptors primarily in the hypothalamus, but also potentially in the pituitary and the testes which can alter gonadal function and mainly affects the hypothalamic-pituitary-gonadal process of controlling the secretion of gonadal hormones testosterone and estrogen, which are necessary for normal sexual and reproductive behavior and growth. When this process functions normally, it begins with the secretion of gonadotrophin-releasing hormone (GNRH) in the hypothalamus and continues with the stimulation of the pituitary gland by the GNRH to secrete luteinizing hormone (LH) and follicle stimulating hormone (FSH). As a result of the two hormones FSH and LH being released into the systemic circulation, interaction between these hormones and the testes and ovaries (gonads) leads to the secretion of testosterone and estrogen that then feed back to the hypothalamus and pituitary forming a complete feedback loop. When the opioids bind to receptors in the hypothalamus, interference with normal release of GNRH has been seen along with a pituitary decrease in the release of LH and FSH. In women, the interference by opioids with the release of LH can negatively affect the menstrual cycle. Opioids have also been seen to directly affect the testes resulting in a decrease in secretion of the testosterone hormone. Some of the symptoms resulting from hypogonadism (inadequate production of sex hormones) include loss of sex drive, infertility, depression, fatigue, and osteoporosis.

Another adverse effect of opioids on the endocrine system would be decreased adrenal androgen production. Androgens are defined as testosterone or a related steroid hormone which is mainly responsible for stimulating changes that are somatic at puberty in males and females along with stimulating the adult sex drive in males and females, and finally stimulating the development of the male anatomy in the fetus and adolescent as well as spermatogenesis. In women, both the adrenal glands and ovaries play an important role in the overall production of androgens. Dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulfate (DHEAS), and androstenedione are the three major adrenal hormones secreted by the adrenal glands in sync with the secretion of cortisol which is in response corticotropin. Daily use of opioids will decrease the production of adrenal androgens,