Pituitary gland Anterior lobe

Somatotropin (growth hormone) STH Pituitary gland, anterior lobe Growth and metabolism... 

Thyrotropin TSH Pituitary gland, anterior lobe Stimulation of thyroid gland... 

Figure 3.2 The pituitary gland is a pea size gland located at the base of the human brain. The pituitary gland has two rounded projections or lobes. Cells of the anterior lobe produce growth hormone and five other protein hormones involved in regulating various body functions, when stimulated by specific signals from the hypothalamus. The optic chiasma is where the optic nerves from each eye cross before entering the brain.

The correlation of the hypothalamus and its hormones with the hormones of the anterior pituitary gland is summarized in figure 5.2. There is no direct vascular connection between the hypothalamus and the posterior lobe of the pituitary that would correspond to the portal vein system for the anterior lobe of the gland. Not all hypothalamo-pituitary hormones will be discussed in the subsequent sections. Only those that are well-defined chemical entities or have a direct connection with drug action are considered. 

The pituitary gland is situated in sella turcica or hypophyseal fossa of the sphenoid bone attached to the brain by a stalk which is continuous with the part of brain i.e. hypothalamus and there is a communication between the hypothalamus and the pituitary gland by means of nerve fibres and a complex of blood vessels. Pituitary gland consists of three parts - anterior lobe or adenohypophysis, posterior lobe or neurohypophysis and middle lobe or pars intermedia. 

Anterior lobe of pituitary is the master gland of the endocrine system as a whole because it produces peptide trophic hormones which affect the other ductless/endocrine glands. The anterior lobe secretes the following hormones ... 

The secretion is stimulated by ACTH from the anterior lobe of pituitary gland. Cortisone and hydrocortisone are the main glucocorticoids and their main function is to regulate carbohydrate metabolism. 

The control of metabolism, growth, and reproduction is mediated by a combination of neural and endocrine systems located in the hypothalamus and pituitary gland. The pituitary weighs about 0.6 g and rests at the base of the brain in the bony sella turcica near the optic chiasm and the cavernous sinuses. The pituitary consists of an anterior lobe (adenohypophysis) and a posterior lobe (neurohypophysis) (Figure 37-1). It is connected to the overlying hypothalamus... 

The pituitary gland is composed of anterior and posterior lobes that are attached to the hypothalamus via the infundibulum or hypophyseal stalk, which includes the portal vessels. Processes from GnRH cells in the hypothalamus terminate on or in the vicinity of the portal vessels that convey blood to the anterior lobe of the pituitary. The... 

Figure 30-1 (A) Median sagittal section of the human brain. From Maya Pines.15 (B) Drawing illustrating the synthesis of peptide hormones in the hypothalamus and transport via portal blood vessels into the anterior lobe of the pituitary gland or via nerve tracts into the posterior lobe.16...

Connected to the brain by a stalk (Fig. 30-1), the pituitary gland releases at least ten peptide or protein hormones that regulate the activity of other endocrine (hormone-producing) glands in distant parts of the body. The pituitary is composed of several distinct parts the anterior lobe (adenohypophysis), a thin intermediate portion (pars intermedia), and a posterior lobe (neurohypophysis). Each has its own characteristic endocrine functions. 

Thyrotropin-releasing hormone is one of several small peptide hormones secreted by the anterior lobe of the pituitary gland. These are the master" hormones that function to stimulate hormone secretion from other endocrine glands. Thyrotropin stimulates the functioning of the thyroid gland. 

Following messenger formation, the amount and types of proteins can be modulated in additional ways. The initial polypeptide can be processed in various ways so that different polypeptides or proteins are expressed in different tissues. Such a situation exists for processing the precursor polypeptide preproopiomelanocortin (see fig. 24.7). This polypeptide is processed in different ways in the anterior and intermediate lobes of the pituitary gland to give rise to different hormones in these two tissues. 

Commentary The DA Dopamine Receptor in the Anterior and Intermediate Lobes of the Pituitary Gland... 

Dopamine can thus be added to the list of hormones and neurotransmitters which can stimulate or inhibit cyclic AMP formation, depending upon their tissue of action. Thus, while dopamine stimulates cyclic AMP formation in parathyroid cells, superior cervical ganglia, retina and striatal tissue (27, 58-61), it inhibits the accumulation of the cyclic nucleotide in cells of the intermediate and anterior lobes of the pituitary gland. Opposite effects on the cyclic AMP system are also found with LHRH which stimulates and inhibits cyclic AMP levels in the anterior pituitary gland (62) and ovary (63), respectively. Similarly, alpha-adrenergic agents show opposite effects on cyclic AMP formation in brain (64) and platelets (65). PGE, stimulates cyclic AMP formation in the anterior pituitary gland (62) while it inhibits the same parameter in fat cells (66). 

ACTH (adrenocorticotropic hormone, corticotropin) is a 39-amino-acid peptide synthesized and secreted by the corticotrope cells of the anterior lobe of the pituitary gland. ACTH acts on several target tissues, including the adrenal cortex, adipose tissue and brain. It is synthesized as part of proopiomelanocortin (POMC) as amino acids 132-170 of this molecule, which is proteolytically cleaved to produce ACTH [1],... 

Smelik PG, Berkenbosch F, Vermes I, Tilders FJH (1983) The role of catecholamines in the control of the secretion of pro-opiocortin-derived peptides from the anterior and intermediate lobes and its implications in the response to stress. In Bhatnagar AS (Ed), The Anterior Pituitary Gland, pp. 113-125. Raven Press, New York. 

The pituitary gland (hypophysis) is located at the base of the skull (Figure 50-1) in a bone cavity called the sella turcica (Turkish saddle). The gland is small—1 cm or less in height and width and weighs approximately 500 mg. As discussed previously, the gland is anatomically divided into the anterior (adenohypophysis) and the posterior (neurohypoph-ysis) lobes. A third lobe (the intermediate lobe) is present in most vertebrates and in the human fetus this lobe is rudimentary in the adult human. 

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