Background: The use of strong opioids for treatment of noncancer chronic pain has increased. However, strong evidence for sustained pain relief and improved function is lacking. Controversy prevails, whether hormonal changes are induced by long-term treatment with opioids. The purpose of this study was to investigate the occurrence of endocrine dysfunction in chronic pain patients on long-term opioid treatment.
Methods: A study group of 39 chronic pain patients treated with strong oral opioids for more than 1 year was compared with a control group of 20 chronic pain patients without opioid treatment. Basic levels of prolactin and function of the hypothalamic-pituitary-thyroid-, hypothalamic-pituitary-adrenal-axis, and hypothalamic-pituitary-growth-hormone - and hypothalamic-pituitary-gonadal-axis were measured. Quality-of-life and side effects were estimated with EORTC-QLQ-C30.
Results: In the opioid-treated group, the patients had signs of pituitary dysfunction affecting all axes. Significant differences were shown in hypofunction of the hypothalamic-pituitary-gonadal -axis, hyperfunction of the hypothalamic-pituitary-adrenal -axis, and higher prolactin levels in the opioid-treated group, compared with the control group. The degree of pain was rated the same in both groups, but the opioid-treated group reported more side effects and lower quality of life.
Conclusions: Long-term treatment of chronic pain with strong opioids causes side effects that can be attributed to hormonal abnormalities caused by opioid-induced inhibition of hypothalamic-pituitary function. Hormone substitution can be indicated to treat symptoms. Decreasing the opioid dose or stopping the opioid treatment can reverse endocrine dysfunction. This needs to be recognized by all practitioners treating chronic pain patients with opioids.