[Circadian rhythm of melatonin in liver cirrhosis]

The liver plays an important role in the intermediate metabolism of numerous substances involved in hormonal action. Starting from the presupposition that the pineal has an inhibitory effect on the reproduction system through melatonin (aMT) and that hepatic cirrhosis can be included among the pathologies characterised by sexual disorders, the authors felt that it was interesting to evaluate the light/darkness rhythm of aMT in some patients suffering from hepatic cirrhosis in order to highlight the possible pathogenetic role of aMT in causing the altered sexual activity observed in this pathology. A total of 4 subjects (3 males and 1 female), with a mean age of 60.5 years, suffering from hepatic cirrhosis and a matched group of healthy controls were included in the study. Circadian changes in aMT plasma levels and plasma levels before and after TRH stimulus (200 micrograms) of aMT and PRL were studied in all subjects. The results revealed the presence of a circadian rhythm of aMT with a nocturnal peak secretion in both groups; in patients with cirrhosis, however, the rhythm appeared to be "out of phase" and presented a late and prolonged increase in aMT compared to controls. Responses to TRH did not show any differences in aMT between the two groups, but the response to PRL was higher and longer than in hepatopathic patients. These findings showed an alteration in the secretory pattern of aMT in cirrhotic patients which can be attributed to reduced hormone metabolism at an hepatic level. The altered response to PRL is attributable to an altered neurotransmitter function at the central level.