Although there is an increasing evidence that the pineal gland may play a role in human malignancy, the studies on melatonin concentrations in different types of malignant tumors brought about controversial results. However, changes in melatonin concentrations have been observed in some types of human malignant tumors. Therefore, we decided to study the circadian melatonin rhythm in patients suffering from cervical cancer in different stages of progression and to compare them with those in subjects free from neoplastic disease. A total of 45 women were analyzed in this study. The subjects were divided into two groups. The first group consisted of 31 patients [mean age 52.1 +/- 1.8 yr (mean +/- S.E.M.), range 32-77 yr] with cervical cancer in various stages of the disease. The second group consisted of 14 healthy volunteers [mean age 53.5 +/- 2.0 yr (mean +/- S.E.M.), range 42-63] who served as the control group. Blood samples were collected at 08:00, 12:00, 16:00, 20:00, 22:00, 24:00, 02:00, 04:00, 06:00, and 08:00 hours. Melatonin concentration was measured by immunoenzymatic method. There were significant differences in circadian melatonin profiles as well as in the area under curve among the two studied groups. Melatonin concentrations were significantly lower in cancer patients in comparison with healthy individuals. Taking into consideration stage of the cervical cancer significantly lower melatonin secretion has been found in all subgroups of patients in comparison with that of tumor-free control group. Additionally, nocturnal melatonin concentrations as well as area under curve were significantly lower in advanced stage of cancer (stages 3 and 4) in comparison with patients with preinvasive cancer (stage 0) at 24:00, 02:00, and 04:00 hours and patients with stage 1 disease at 02:00 and 04:00 hours. The results of the present study indicate that the presence of cervical cancer influences melatonin levels in women. Moreover, stage dependence in reduction of melatonin concentrations has been found.

Diurnal rhythm of serum melatonin concentrations was estimated in 12 men with low back pain syndrome before and after exposure to a very low-frequency magnetic field (2.9 mT, 40 Hz, square wave, bipolar). Patients were exposed to the magnetic field for 3 weeks (20 min per day, 5 days per week) either in the morning (at 10:00 hr) or in the late afternoon (at 18:00 hr). Significant depression in nocturnal melatonin rise was observed regardless of the time of exposure. This phenomenon was characteristic for all the subjects, although the percent of inhibition of melatonin secretion varied among the studied individuals.

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Patients with neuroendocrine tumors (NETs), malignancies of rare but still rising incidence, may be a group at higher risk of vitamin D insufficiency. The gastrointestinal tumor prevalence and somatostatin analog (SSA) therapy may cause vitamin D malabsorption. The aim of this study was to evaluate the serum level of vitamin D in NET patients. A total of 36 NET patients were enrolled into the experimental group and 16 individuals were enrolled into the control group. All patients were further classified into subgroups according to primary tumor localization (gastropancreatic, lung, and other NETs) or therapy (with or without SSA treatment). The concentrations of total 25(OH)D were assayed with Electrochemiluminescence immunoassay (ECLIA). Serum concentration of 25(OH)D in NET patients did not differ significantly from that of the control group. However, the average level of 25(OH)D in both groups met the criteria of vitamin D deficiency. Importantly, SSA therapy did not aggravate vitamin D deficiency. Moreover, the concentration of 25(OH)D in the studied group was not significantly influenced by primary tumor localization, patient age, or season. Vitamin D deficiency is a widespread disorder affecting both NET patients and individuals without other health problems, and SSA and gastrointestinal tumor localization do not exacerbate this condition.

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