The thyroid gland produces several hormones which, like all hormones, are released into the blood in which they are carried to their sites of action in other parts of the body. The rate of secretion of these hormones is regulated primarily by another hormone secreted by the anterior pituitary gland. In addition, it has very recently been recognized that thyroid nerves may also play some role in regulating several aspects of thyroid hormones. Recent preliminary studies in the PIs' laboratory and elsewhere indicate that these neuropeptides have dramatic effects on thyroid blood flow and thyroid hormone secretion. The present experiments are designed to determine the physiological significance and the endogenous neuropeptides occurring in the thyroid nerves. One part of this project consists of experiments in which the effectiveness of endogenous pools of neuropeptides play a physiological role in regulating normal thyroid function. In the second part of this project, changes in thyroid blood flow and/or thyroid hormone secretion will be induced followed by the determination of whether there are associated changes in the size or the rate of turnover of the endogenous neuropeptide pools. Such changes would also support the notion that these peptides are important in the normal regulation of thyroid function. The neuropeptides studied in this project are known to occur in many normal tissues and numerous tumors, but very little is yet known of their functional importance.
