Endocrine Abstracts

Objective: Exogenous and endogenous opioids affect the hypothalamic–pituitary–gonadal axis through binding to receptors centrally and by peripheral inhibition of testosterone synthesis, thereby altering the release of hormones. Approximately 12% of patients with persistent non-cancer pain use strong opioid analgesics in the UK, but the action on endocrine function may not be recognised. The aim of this study is to establish the incidence of gonadotrophin and other endocrine dysfunction in patients using opioids for persistent non-cancer pain who attended an inner city pain clinic.

Methods: We randomly analysed 34 patients on long-term opioids. All patients were using oral, transdermal, or intrathecal opioids; the duration varied between 6 months and 20 years.

Early morning blood samples were obtained measuring: LH, FSH, testosterone, cortisol, prolactin, oestradiol, and thyroid function.

Results: Eighty percentage of the male patients were found to have low testosterone with a mean testosterone of 3.5 nmol/l, range 0.5–7 nmol/l; the LH and FSH were disproportionally low in all these patients. Mean LH 2.8 U/l, range (0.1–5.1), S.D. of the mean 2.4; mean FSH 4.3 U/l, S.D. of the mean 4.7.

Seventy-one percentage of the female patients had undetectable oestradiol <60 pmol/l with a mean of 75 pmol/l and S.D. of mean 26.

Abnormal 0900 h cortisol was observed in 30% of patients; range 30–92 nmol/l. No thyroid or prolactin abnormality was detected.

Conclusion: We demonstrated that long-term opioid use is associated with pituitary hormone disturbance. The effect is more profound on gonadotrophins through the inhibition of hypothalamic GnRH. We also observed that opioid use may be associated with a decrease in cortisol level as seen in 30% of our patients. It is imperative that patients on long-term opioids have routine anterior pituitary hormone assessments.