ABSTRACT
In any consideration of the endocrine system, it is necessary to draw attention not only to the overall control of this system but also to how the various organs that together constitute this system interact to control homeostasis. Possibly of greatest importance involves the control of anterior pituitary hormone secretion by the hypothalamus. General observations on the clinical relationship between these two structures have long been known, and examples are provided, where appropriate, throughout the text. As the terminology used for describing the development and various components of the pituitary gland often depends on the species studied and source of information, it was considered useful to provide information on this topic at an early stage in this chapter.1−7
It is now also appreciated that the hypothalamus controls the anterior pituitary gland via the pituitary portal venous system. By this means, the median eminence of the hypothalamus is now known to be closely associated with the anterior part of the pituitary gland. As a result of numerous largely experimental studies, it now appears clear that the hypothalamus controls the anterior pituitary indirectly via chemotransmitters that are mediated through the hypothalamo-pituitary portal venous system. Of critical importance would appear to be an understanding of the role of certain releasing factors produced by the hypothalamus and how they act via the pituitary gland. By this means, the control of a wide range of bodily functions is achieved. For example, these releasing factors are now known to play a critical role in the control of reproduction, growth, and development as well as in the maintenance of fluid balance and the control of the body’s response to stress. These functions are all achieved through the control of pituitary hormone production by the hypothalamus. For observations on the interrelationship between the hypothalamus and pituitary and how neural control of glandular secretion is achieved, see Cone et al.2,8
The intimate relationship that is established between the hypothalamus and pituitary gland occurs at a very early stage of mammalian development, and how this arises in the human, the mouse, and to a lesser extent in the rat is considered in this chapter.
