INTRODUCTION The basis of secretions of endocrine gland, mechanism of hormone actions, hormone secretion and actions of hormones secreted by anterior, intermediate and posterior lobe of pituitary gland, hormonal level and hypothalamic control of hormone secretion and pathological diseases related to abnormal hormone secretion will be discussed in the chapter. Detailed account of physiology of growth hormone, vasopressin and oxytocin should be meticulously learned The glands of the body may be divided into those with an internal secretion (endocrine glands) and those with an external secretion (exocrine glands). Examples of exocrine glands are the sweat, lacrimal and mammary glands which pass their secretion along ducts to the external surface of the body, and the glands of the mouth, stomach and intestines whose secretions are passed along ducts into the alimentary tract. On the other hand, the endocrine (ductless) glands do not possess any ducts or openings to the exterior. Two systems are empowered with this act of coordination for body to function as a harmonious unit; they are the nervous and endocrine systems. The endocrine (Greek, endon = within; crinein = to set apart) system consists of a number of ductless glands (Fig. 70.1) which manufacture certain chemical Hypothalamus Pituitary Anterior lobe Posterior lobe Endocrine glands produce hormones (chemical messengers) which are passed into blood stream for general circulation to excite or inhibit activities of other organs or tissues.