Chronic spinal and oral morphine-induced neuroendocrine and metabolic changes in noncancer pain patients

Interactions between opioid use and hormonal function are documented in the literature. However, it is unclear if therapeutic intrathecal opioid therapy can induce hormonal changes, compared to oral opioid therapy.

The authors studied hormone and metabolic changes in 22 women (18-60 years) and 38 men (18-45 years) who were referred to a pain center. The patients were allocated to different treatment groups (based on assistant physicians' decision), as follows: 20 patients received oral morphine (60-120 mg/day); 20 patients, spinal morphine (0.2-10 mg/day); and 20 patients, nonopioid analgesic treatment.

All three groups experienced substantial improvement in pain scores during the whole follow-up period. Significantly impaired libido, reduced potency, hot flashes, and menstrual cycle dysfunction occurred more often in both morphine groups than in the nonopioid group. Significantly low serum total testosterone levels were more prevalent in the spinal morphine group and the oral morphine group (58.3% and 70.0%, respectively) than in the control group (16.7%). Total cholesterol values above 200 mg/dL and higher ultrasensitive C-reactive protein levels were significantly more frequent in the morphine groups than in the controls. Total body bone mineral density was below normal in men receiving spinal morphine (P = 0.014).

Hypogonadotrophic hypogonadism was more prevalent in the morphine groups and was correlated with clinical findings. Significant bone mass loss occurred in morphine users, even without hormone dysfunction when compared to nonopioid treatment. Growth hormone, thyroid stimulating hormone, adrenocorticotrophic hormones, and cardiovascular risk parameters were less compromised in morphine users.