The Influence of Acute Cerebral Infarction on the Circadian Rhythm of Melatonin Secretion

ABSTRACT

BACKGROUND: The circadian rhythm of circulating melatonin is regulated by the endogenous oscillators, the suprachi-asmatic nuclei, and entrained by the light-dark cycle of the environment, but it seems that the rhythm can be affected by variable lesions outside the retina-pineal pathway. We intended to know how acute cerebral infarction affects on the cir-cadian rhythm of plasma melatonin secretion. METHODS: Plasma melatonin level was measured from 64 patients with acute cerebral infarction. On admission, blood samples were collected by venipuncture at 2AM, 4AM, 10AM, and 2PM and melatonin level was measured by radioimmunoassay. The state of consciousness of each patient was assessed clini-cally and the infarction site and size were evaluated clinically and radiographically. RESULTS: Among 64 patients with acute cerebral infarction, dramatic blunting or obliteration of nocturnal melatonin surge in the blood was found in 29 patients. The circadian rhythm of melatonin secretion was absent in 12 of 35 alert patients, in 10 of 20 drowsy patients, and in 5 of 7 stuporous patients. Melatonin secretion into plasma was markedly decreased in all 2 comatose patients. Of 14 patients with brainstem lesions, 8 patients showed decreased melatonin levels with the absence of a nocturnal rise, although most of them were alert. CONCLUSIONS: This study suggests that brainstem and the initial mental state might contribute to the regulation of the circadian rhythm of plasma melatonin even though the lesion does not involve the retina-pineal pathway, but further extensive study is required to elucidate it. (J Korean Neurol Assoc 19(4)359~363, 2001)