24 HOUR RHYTHM OF MELATONIN IN PATIENTS WITH A HISTORY OF PINEAL AND OR HYPOTHALAMONEUROHYPOPHYSEAL GERMINOMA/

Melatonin deficiency after a pinealectomy has been investigated in ani mals; however, in humans, this status can be assessed solely by invest igating patients with a tumor originating in the pineal gland. This st udy analyzes secretion of melatonin and pituitary hormones in 14 patie nts with germinoma originating in the pineal or the hypothalamic-neuro hypophyseal region. Thirteen patients had been successfully treated pr ior to this study. One patient was included in this study before the i nitiation of treatments. Plasma sampling was performed every 2 hr for 24 hr and melatonin concentrations were measured by radioimmunoassay. Melatonin secretion was nearly absent in the patients with pineal germ inoma regardless of treatment option, even in the patient who had been untreated. In contrast, melatonin secretion and its circadian rhythms were not affected in patients with a hypothalamo-neurohypophyseal ger minoma. The circadian rhythms of growth hormone and adrenocorticotropi c hormone were not dysregulated in patients with the melatonin deficie ncy. We conclude that germinoma cells originating the pineal gland imp air the production of melatonin by pineocytes and consequently induce a permanent melatonin deficiency in those patients. Since melatonin ex erts multiple physiological functions, once a clinical concept of ''me latonin deficiency syndrome'' is established, melatonin replacement th erapy could be investigated in patients who have a pineal germinoma or who have undergone a neurosurgical pinealectomy.