Recent studies have shown that the hematopoietic system is under neuroendocrine control. In particular, thrombopoiesis has been proven to be stimulated by
melatonin, and the pineal
indole has been shown to be effective in the treatment of
thrombocytopenia resulting from different causes. At present, however, there are no data concerning the possible thrombopoietic activity of pineal
indoles other than
melatonin. The present study was carried out to evaluate the effect of a concomitant administration of the pineal
indole 5-methoxytryptamine in patients with
cancer-related
thrombocytopenia who did not respond to
melatonin alone. The present study included 30 patients, who were randomized to receive
melatonin alone (20 mg/day orally in the evening) or
melatonin plus
5-methoxytryptamine (1 mg/day orally in the early afternoon). A normalization of platelet count was achieved in 5/14 (36%) patients treated with
melatonin plus
5-methoxytryptamine and in none of the patients treated with
melatonin alone (P < 0.05). Moreover, mean platelet number significantly increased only in the patients treated with
melatonin plus
5-methoxytryptamine. This preliminary clinical study would suggest that
5-methoxytryptamine, a pineal
indole, may also exert thrombopoietic activity. Further studies, however, will be required to establish whether
5-methoxytryptamine may play a direct thrombopoietic activity, or whether it may act by improving
melatonin's efficacy.