Current problems in the clinical physiology of the parathyroid and thyroid glands.

TO the investigator concerned with the fundamental aspects of endocrine control mechanisms and the practical application of such knowledge, regulation of the secretion of the parathyroid and thyroid glands offers much that is both challenging and new, and also lends itself easily to further development. One need look no further than the recent discovery of thyrocalcitonin for an example of contemporary endocrinological research which has provided not ‘only obvious therapeutic advantages (such as the management of hyperparathyroid or hypercalcemic “crisis”), but also appears likely to be a key to the understanding of parathyroid control mechanisms which heretofore have uniformly thwarted investigators working in this area. In a more methodical but no less compelling way, evidence of the participation of the central nervous system in the stimulation and inhibition of thyroid hormone secretion makes it clear that there is a more mature and inclusive control of thyroid secretion than the conventional pituitary feedback mechanism. This is important not only for its own sake, but also as a model of ‘organization that can be applied to other endocrine systems previously considered to be under exclusive feedback control of the pituitary gland. That therapeutic advances may develop from such basic information seems highly likely. This