[Effect of deficiency and excess of thyroid hormones in the body on indolamine metabolism in the rat epiphysis cerebri].

Thyroid hormones were demonstrated to play a role in serotonin metabolism control in pinealocytes. Saturation of the body with T4 shifts the process of serotonin utilization toward acetylation and subsequent ortho-methylation with primary formation of N-acetylserotonin and melatonin while total thyroidectomy blocks this process to a considerable degree. Under deficiency of thyroid hormones the pathway of oxidative serotonin deamination with primary formation of 5-hydroxyindole-acetic acid is the predominant one. Excess and deficiency of thyroid hormones produce opposite effects in the epiphysis. The data obtained not only support the presence of the negative feed-back in the epiphysis-thyroid system but also emphasize that the process of formation of epiphyseal methoxyindoles is the most sensitive one to the action of thyroid hormones.