Neuroendocrinology of pyridoxine deficiency.

Dihydroxyphenylalanine decarboxylase and 5-hydroxytryptophan decarboxylase respectively have high and low affinities for pyridoxal phosphate. In the pyridoxine-deficient animal, hypothalamic serotonin content is significantly reduced without any change in catecholamine levels. Hypothalamic neurotransmitters affect the hypothalamo-pituitary-end organ axes. Specifically, the decrease in hypothalamic serotonin in the pyridoxine-deficient rat results in tertiary hypothyroidism. In addition, pineal function is affected in deficient animals due to decreased synthesis of melatonin.