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Abstract
To the Editor: The role of monoamines in control of the secretion of anterior pituitary hormones has been widely studied in the past few years.1 The hypothalamic dopaminergic pathways have been shown to be involved in the regulation of prolactin, growth hormone, ACTH, and gonadotropins.2 Pyridoxine (vitamin B6 ) is one of the natural precursors of pyridoxal-5'-phosphate coenzyme in the decarboxylation and transamination of amino acids. [...]this drug has been reported to reduce prolactin levels and raise growth hormone levels,3 although this action has not been confirmed.4 We conducted a study to evaluate the effect of pyridoxine on prolactin and growth hormone levels during exercise, since exercise provides a good model for the physiologic release of the adenohypophyseal hormones.5, 6 Six healthy subjects 25±3 years old volunteered to enter the study. After blood collection the test tubes were placed on ice; the plasma was immediately separated and frozen at -70°C. Levels of growth hormone and prolactin were measured by means of sensitive and specific radioimmunoassays.7 The results, analyzed with Student's t-test, are shown in Table 1.