Medical Research

Glands, Peptides, Hormones and Growth Factors

Glands are collections of hormone secreting cells that are located in various regions of the body. Collectively the glands make up the endocrine system. Each gland secretes specific chemicals known as hormones that function to regulate and maintain the internal environment and promote the survival of the organism. The glandular release of hormones is part of a chemical communication and control system that augments and works in tandem with the neural communication and control systems within the body. Hormones are chemical signaling molecules that are produced in one site of the body and then travel to other areas of the body where they have their effect. Hormones may be peptides, proteins, or steroids. Growth factors are small polypeptides created by many different types of cells and generally act locally.

The pituitary gland has often been called the ‘Master Gland’ because the hormones it releases control the release of hormones from other glands. However, the pituitary itself is controlled by a brain area called the hypothalamus, which discharges special peptides called releasing factors into a local blood vessel network (hypothalamic-hypophyseal portal system) that feeds the pituitary cells. The releasing factors of the hypothalamus then initiate or inhibit the release of pituitary hormones, which travel via the circulatory system to target tissues throughout the body. The pituitary can be divided into three portions: the anterior pituitary, the intermediate lobe, and the posterior pituitary. While six peptide hormones are secreted by the anterior pituitary: growth hormone (somatotropin), corticotrophin (ACTH), thyroid-stimulating hormone (TSH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), and prolactin, for brevity this guide will focus on a hormone called growth hormone (GH) and a peptide known as fibroblastic growth factor.

GH affects all cells of the human body. GH produces its growth enhancing and metabolic effects by binding to a specific cell membrane receptor that is distributed in tissues throughout the body. It is named GH because it is necessary for the growing child, but it remains essential for normal body functions throughout life. From an adult point of view, GH is misnamed. Instead it should be called cell rejuvenation factor.

 

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