Relationship between Pineal Gland and Opioid System in Cancer Patients

Abstract

Recent studies showed that the pineal gland and endogeneous opioids are involved in the modulation of immune system activity and in the regulation of tumour growth. Moreover, a relationship between the pineal gland and the opioid system has been demonstrated. In order to establish whether the anomalous secretion, observed in human neoplasms, may be correlated to an altered pineal-opioid relationship, serum levels of melatonin and β-endorphin and their light/dark rhythm were evaluated in oncological patients. Furthermore, growth hormone (GH), prolactin (PRL), follicle stimulating hormone (FSH), luteinizing hormone (LH), Cortisol and melatonin response to FK 33 – 824, a met-enkephalin analogue, were determined in patients with early or advanved neoplastic disease. Serum levels of β-endorphin were found to be within the normal range in patients suffering from cancer, while the serum levels of melatonin were elevated in several cases. An anomalous circadian rhythm of melatonin levels in the serum was seen in 46.2% of the patients whereas 73.1% of the patients had anomalous circadian rhythms of serum levels of β-endorphin. After FK 33 – 824 infusion an altered response of GH, PRL and LH circulating levels was observed in all oncological patients, an altered response of melatonin was observed in 10 out of 14 patients. These findings suggest the existence of an altered pineal-opioid system relationship in human neoplasm.