A. Ariav Albala

Morphine inhibits cortisol and stimulates prolactin secretion in man

The role of opioids in endocrine regulation has been the subject of numerous studies. Surprisingly, however, the acute endocrine effects of morphine on basal hormonal levels in man have not been adequately documented. We report here the effects of intravenous morphine (5 mg) on plasma cortisol and prolactin. Fourteen healthy volunteers (nine male, five female) received morphine at 0930 hr. Blood samples were collected immediately before and 30, 60, 90, 120 and 180 min after the injection. In six of the male subjects the procedure was repeated with a placebo (normal saline) injection. Morphine stimulated prolactin release. There was a trend for a greater response in females compared to male subjects. Cortisol secretion was markedly suppressed by morphine. In sharp contrast to the results obtained with placebo, cortisol levels following morphine declined progressively at a rate consistent with the half-life of cortisol. This downward trend of cortisol values continued uninterrupted for the duration of the experiment in all 14 subjects. These results are consistent with the presence of an inhibitory opioid mechanism in the human hypothalamo-pituitary-adrenal axis.

Dexamethasone suppression test and selection of antidepressant medications

Endogenous depressives with abnormal dexamethasone suppression tests (DSTs) respond better to somatic antidepressant treatments than those with normal DSTs. Whether the DST also aids in the selection of specific antidepressants has not been determined. A pilot report suggested that patients with abnormal DSTs might be noradrenaline-deficient and respond preferentially to imipramine or desipramine, whereas those with normal DSTs might be serotonin-deficient and respond best to amitriptyline or clomipramine. Attempting to replicate this observation, we studied 26 patients diagnosed with Research Diagnostic Criteria as major depressive disorder, endogenous subtype, and with DSM-III as having melancholia. All were drug-free during baseline evaluation. All had abnormal DST results, with post-dexamethasone plasma cortisol levels exceeding 5 microgram/dl. We treated subjects with either imipramine or amitriptyline and compared clinical response with weekly Hamilton Depression Rating Scales, completed by raters blind to both DST results and the research question. Thereapeutic plasma levels were documented. We found no significant differences in treatment response between the subgroups. Twenty of the 26 subjects did well. The imipramine-treatment group failed to have either earlier response or better final outcome. These data fail to replicate suggestions that DST results assist in the selection of either imipramine or amitriptyline.

Prolactin response to morphine in depression

Twenty-two unmedicated inpatients with major depression and 18 healthy volunteers of either sex were given an intravenous injection of 5 mg morphine. Blood samples were drawn immediately before and at intervals for 3 hrs after the injection and assayed for prolactin. Morphine stimulated prolactin secretion. The prolactin response of females was significantly greater than the response of male subjects. There were no significant differences in the prolactin response to morphine between depressed and healthy subjects. The implications of these findings for the hypothesized role of the opioid system in the pathophysiology of depression are discussed.

Hormone response to repeated electroconvulsive therapy: Effects of naloxone

Plasma prolactin (PRL), cortisol, and growth hormone (GH) were measured before, and at 15-min intervals for 1 hr after, electroconvulsive therapy (ECT). This was repeated over a series of 6 consecutive treatments for each of 12 depressed drug-free inpatients. Patients received naloxone, 2 mg or 20 mg, by intravenous infusion before the third and fifth treatment. ECT was consistently followed by a release of PRL and cortisol, although two patterns of PRL response could be distinguished. In eight patients, the PRL response did not change significantly with repeated ECT, whereas in four patients, the plasma PRL increased tenfold after the first treatment and decreased after each successive treatment. The GH level varied widely, with no evidence of a reliable response to ECT. Opiate receptor blockade with low- or high-dose naloxone did not alter the release of PRL or cortisol after ECT. These findings demonstrate a reliable PRL and cortisol response to ECT, but do not support a role for endogenous opiates in these hormonal changes.

Prolactin response to TRH in depression

We studied the prolactin response to TRH in 53 unmedicated psychiatric inpatients. The prolactin response of females was significantly greater than the response of male subjects. There was no significant difference in the prolactin response to TRH between depressed patients and those with other psychiatric diagnoses. There was no significant relationship between the prolactin response to TRH and the severity of depression, the TSH response to TRH or the resistance to suppression of cortisol secretion by dexamethasone.

Comparison of early and delayed inpatient dexamethasone suppression tests

Ninety-five inpatients completed a dexamethasone suppression test (DST) within 72 hours after admission and again after at least 1 week of medication-free hospital care. The frequency of cortisol nonsuppression in patients with endogenous depression (ED) was high and not significantly different at both tests. In patients with diagnoses other than ED, the higher rate of cortisol nonsuppression at the first DST was associated with a significant decrease in test specificity. Change in postdexamethasone cortisol levels at repeat testing was associated with a decrease in depressive symptomatology, but was not related to weight change during hospitalization.

Cortisol escape from morphine suppression

Twenty-one unmedicated, sequentially admitted psychiatric patients of either sex and four male healthy volunteers were given an intravenous injection of 2.5 mg morphine. Blood samples were drawn immediately before and at 30-minute intervals for 3 hours after the injection and assayed for cortisol. Morphine suppressed cortisol secretion. Early resumption of cortisol secretion (escape) was more frequent in patients with a diagnosis of major depressive disorder and with abnormal dexamethasone suppression test results. The sensitivity of this infusion paradigm for the diagnosis of major depressive disorder was 40%, and the specificity was 82%. The implications of these findings for the pathophysiology of depression are discussed.

Escape from dexamethasone suppression: Possible role of an impaired inhibitory opioid mechanism

Several lines of evidence indicate that the activity of the hypothalamus-pituitary-adrenal (HPA) axis in depression is disinhibited. Escape from dexamethasone suppression, although not limited to is more frequent in patients with endogenous depression compared to normals or patients with other psychiatric diagnoses. Norepinephrine, serotonin and acetylcholine have been implicated in the pathophysiology of this neuroendocrine abnormality. Morphine, 5 mg intravenously, suppressed cortisol secretion in healthy volunteers (n = 4) and the majority of 32 psychiatric inpatients. However, patients with endogenous depression and abnormal dexamethasone suppression test results show early resumption (escape) of cortisol secretion following the initial suppression induced by morphine. It is concluded that the pathophysiology of this neuroendocrine abnormality is not limited to classical neurotransmitter-HPA axis interaction but that it also involves opioid inhibitory mechanisms.