Twenty-four hour rhythm of melatonin in patients with a history of pineal and/or hypothalamo-neurohypophyseal germinoma.

Melatonin deficiency after a pinealectomy has been investigated in animals; however, in humans, this status can be assessed solely by investigating patients with a tumor originating in the pineal gland. This study analyzes secretion of melatonin and pituitary hormones in 14 patients with germinoma originating in the pineal or the hypothalamic-neurohypophyseal region. Thirteen patients had been successfully treated prior to this study. One patient was included in this study before the initiation 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 germinoma 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 germinoma. The circadian rhythms of growth hormone and adrenocorticotropic hormone were not dysregulated in patients with the melatonin deficiency. We conclude that germinoma cells originating the pineal gland impair the production of melatonin by pineocytes and consequently induce a permanent melatonin deficiency in those patients. Since melatonin exerts multiple physiological functions, once a clinical concept of "melatonin deficiency syndrome" is established, melatonin replacement therapy could be investigated in patients who have a pineal germinoma or who have undergone a neurosurgical pinealectomy.