Evidence for Modulation of Melatonin Secretion in Men With Benign and Malignant Tumors of the Prostate: Relationship With the Pituitary Hormones

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Abstract
Serum levels of the pineal hormone melatonin were determined by radioimmunoassay (RIA) in 4 h intervals throughout a 24 h period in elderly men with different types of prostate tumors: benign prostatic hyperplasia (BPH, n = 13), incidental carcinoma (PCi, n = 5) and nonmetastasizing carcinoma (PC, n = 9) and in young men (YM, n = 10). Simultaneously, the pituitary hormones prolactin, growth hormone, luteinizing hormone and FSH were measured by RIA. All subjects were untreated and free of serious complaints and stayed in the same enviroment. Data were analyzed by the population mean-cosinor method; linear correlation coefficients between the 5 hormones were calculated for each group. Melatonin showed significant circadian rhythms in young men and patients with BPH and PCi but not in patients with PC; 24-h mean concentration (mesor) and amplitude were significantly increased in patients with PCi as compared to patients with PC. Prolaction showed significant circadian rhythms in young men and in patients with BPH; patients with PCi and PC appeared to have ultradian variations. Growth hormone did not show significant rhythms in any group; mesors were elevated in all tumor groups as compared to young men. Gonadotropin mesors were elevated in all tumor patients as compared to young men; rhythms were not detected. Carcinoma patients showed different interhormonal correlations than all other groups. Modulation of melatonin secretion, accompanied by changes in the pituitary hormone levels, may evidently be related to development and growth of prostate cancer.