ABSTRACT
The thyroid gland, a key organ in the prenatal and postnatal whole-body growth and differentiation and maturation of the central nervous system, continues to influence the whole organism as it ages, particularly with respect to vital functions such as basal metabolism and thermoregulation. As in the case of other neuroendocrine systems (Chapters 9-11), in this chapter, the thyroid will be examined, first, within the framework of a three level axis, the hypothalamo-pituitary-thyroid axis (HPT). Second, by virtue of their intimate anatomic association with the thyroid gland, changes with aging of the parathyroid cells secreting parathyroid hormone (PTH) and of the thyroid C cells secreting calcitonin (CT) are included in this chapter. Third, also included in this chapter is a discussion of the aging of the pineal gland and its role as a photoneuroendocrine transducer, as a synchronizer of the sleep-wake, and nightday cycles, and as a possible contributor to those homeostatic networks that regulate the life span.
