Experimental studies concerning the mechanism of the thyroid-pineal interrelationship. I. The action of the pineal peptides on the thyroid gland.

Subcutaneous administration of a pineal polypeptide extract, "Crinofizin", to adult male Wistar rats having the thyroid function inhibited by prolonged administration of MTU, has important effects on both the whole organism (slightly correcting the weight increase rate, loweri g cholesterolemia) and the thyroid gland (reducing thyroid hyperplasia and playing a part in various stages of thyroid hormones metabolism). Thus under pineal treatment one can observe a clear tendency to return to the normal values of the thyroid parameters strongly modified by MTU, as RIC, intrathyroid proteic iodine, tissue thyroid hormones distribution, blood PBI and total T4. It appears that these effects of pineal peptides are induced directly on the thyroid and/or via the hypophyso-thyroid axis which they intercept and equilibrate (moderate).