 Dear students, in this topic we shall take an overview of the endocrine glands of vertebrates. The vertebrates have a large number of endocrine glands and tissues that produce hormones. Most of the hormones are produced by only one endocrine gland, which is located at a specific site. However, some hormone-like substances, for example, prostaglandins and leukotrienes, are produced by most or all tissues of the body. And some hormones are produced by more than one specific tissues of the body. We shall take an overview of the vertebrate endocrine glands and the hormones which they produce. First, most important neuroendocrine gland is the hypothalamus. Hypothalamus produces seven hormones which affect the anterior pituitary gland. These hormones are the tropic hormones and have two types of effects. Four hormones have stimulatory effects and three hormones have inhibitory effects on rays of hormones from the pituitary gland. These stimulatory hypothalamic hormones include the carticotropin-releasing hormone, CRH, growth hormone-releasing hormone, gonadotropin-releasing hormone, GNRH, and thyrotropin-releasing hormone, TRH. These hormones affect the anterior pituitary gland to produce the respective hormones. The hypothalamic inhibitory hormones include three hormones, MSH-inhibiting hormone, which is called MIH, prolectin-inhibiting hormone, and somatostatin. These hormones inhibit the secretion of hormones from anterior pituitary. These hormones which are inhibited include the melanocyte-stimulating hormone, prolectin, and growth hormone. Dear students, the anterior pituitary gland produces four types of tropic hormones and three other hormones which are non-tropic in action. Tropic hormones are those hormones which act on other endocrine glands and cause them to produce their own hormones, while non-tropic hormones are those which act directly on the tissues and produce their effects. The pituitary gland has two lobes. The anterior lobe produces four tropic hormones. These hormones include the luteinizing hormone, which acts on the gonads, especially the ovaries, follicle-stimulating hormone that also acts on the gonads and causes them to produce the male and female sex hormones. The third hormone is the thyroid-stimulating hormone, TSH, also called thyrotropin. It stimulates the thyroid gland to produce its hormone. The fourth hormone is the adenocorticotropic hormone, or ACTH, that stimulates the release of cortico-steroids from the adenocortex. The anterior pituitary gland also produces three non-tropic hormones. These include the growth hormone, prolactin, and melanocyte-stimulating hormones. They promote growth, promote production of milk, and stimulate melanin pigment, respectively. Dear students, the posterior lobe of pituitary gland also produces two hormones. These hormones are anti-diuretic hormone and oxytocin. Dear students, next endocrine gland is the thyroid gland. Thyroid gland has two types of glandular cells. The follicular cells, which produce two hormones, thyroxine, and triiodothyronin, while the para-follicular cells of thyroid produce one hormone that is called calcitonin. The next endocrine gland of vertebrates is the para-thyroid gland. This produces one hormone which is called para-thermon. Dear students, the next endocrine gland we will discuss is the adenal gland. There are two types of adenal gland. This is a dual gland. This has adenal cortex and adenal medulla. Adenal cortex produces two types of hormones which are mineralocorticoids and glucocorticoids. Apart from this, we produce more hormones. Most of the glands we are talking about produce more hormones than these. But we are discussing the major hormones. The major hormones of adenal cortex include aldosterone, which is mineralocorticoid, and glucocorticoids, which have three types of hormones, cortisol, cartisone, and carticosterone. They are produced from adenal cortex. Adenal medulla produces two very important hormones, which are epinephrine and nor-epinephrine. They are called catecholamines in a combined form. Dear students, pancreas is a dual gland. It has an exocrine part that produces the digestive pancreatic juice. But it also has islets of Langerhans, which are endocrine in their function. They produce two hormones, insulin and glucagon. The next gland is the pineal gland. Penial gland produces a hormone which is called melatonin and this melatonin is very important in circadian rhythms. Dear students, gonads, in addition to producing gametes, also act as endocrine tissues. The testes produce two types of hormones, testosterone and inhibin, from two types of glandular cells, latic cells and certuli cells. The ovaries produce two major hormones in females. These are estrogen. The major estrogen is the estradiol and the progesterone. Dear students, the placenta which develops during the fetal development also produces many hormones. The two major hormones produced by placenta are corionic gonadotropin and placental lactogen. Dear students, heart is a pumping organ. But its atrium also produces an important hormone which is called atrial natriuretic factor that controls blood volume and pressure. Dear students, the gastrointestinal tract also produces many hormones. These hormones include cholecystokinin, chymodinin, gastrin, secretin, substance P and motilin. Many of these regulate the secretions of digestive juices and enzymes. Dear students, some hormones and hormone-like substances are produced by most or all tissues of the body. These hormones include leukotrienes, prostacycline, prostaglandins and thrombocenes. These control various nucleotide formations and cyclic AMP and cyclic GMPs. The hormones which are produced by more than one selected type of tissues include endorphins, epidermal growth factors, fibroblast growth factor, nerve growth factor and somatomadones. Dear students, from all this list we can conclude that some glands are distinct and are easily identifiable. However, a large number of endocrine tissues are not distinct and are found embedded in the organs which have quite different functions than the endocrine functions. That is why the identification and discovery of endocrine glands has been a challenging task.