Biochemistry of the pineal gland as an endocrine organ.

Experimental studies established a relationship between the pineal gland and various tumors a long time ago. Pineal extracts inhibit a wide spectrum of experimental tumors. Moreover, melatonin shows an anti-tumor action in both intact and pinealectomized animals. We have found that serum melatonin content is increased by 4 to 5-fold in melanoma patients. In normal subjects serum melatonin ranges from 0.47 to 0.65 nmol/l or 1.44 to 2.14 pg/mg serum protein. In contrast, in melanoma patients melatonin content of the serum varies between 2.07 to 6.20 nmol/l or 9.70 to 20.86 pg/mg serum protein. In another study, controls had melatonin levels of 0.47 +/- 0.02 nmol/l serum, or 2.07 +/- 0.24 pg/mg serum protein. In melanoma patients, the melatonin level was 1.65 +/- 0.10 nmol/l serum or 9.82 +/- 1.02 pg/mg protein. Post-mortem examinations revealed that the pineal pigment content was inversely related to the prevalence of malignancy, suggesting that a high melatonin level may be associated with an oncostatic action. Hydroxyindole-O-methyltransferase activity was significantly higher in the pineal gland of subjects that died from malignant tumors as compared with subjects that died from other causes.