Hormones are signaling molecules produced by glands and transported by the circulatory system to target distant organs and regulate physiology and behavior of cells and tissue. Hormones have diverse chemical structures, mainly of 3 classes: eicosanoids, steroids and amino acid derivatives. Alterations in hormone levels have been implicated in obesity, infertility, diabetes, dwarfism, and many, many other disorders. Therefore, the ability to measure changes in hormone concentration in numerous samples could yield valuable insight into these disorders.
Creative diagnostics provides over 400 different hormone ELISA kit with high sensitivity and reliability. The assays can be used for detection of major hormones in serum, such as GDF, hCG, insulin and so on.
For the body to function properly, its various parts and organs must communicate with each other to ensure that a constant internal environment is maintained. Communication among various regions of the body is also essential for enabling the organism to respond appropriately to any changes in the internal and external environments. Two systems help ensure communication: the nervous system and the hormonal system. The nervous system generally allows rapid transmission (i.e., within fractions of seconds) of information between different body regions. Conversely, hormonal communication, which relies on the production and release of hormones from various glands and on the transport of those hormones via the bloodstream, is better suited for situations that require more widespread and longer lasting regulatory actions. Thus, the two communication systems complement each other. In addition, both systems interact: Stimuli from the nervous system can influence the release of certain hormones and vice versa. Generally speaking, hormones control the growth, development, and metabolism of the body; the electrolyte composition of bodily fluids; and reproduction.
Hormones are molecules that are produced by endocrine glands, including the hypothalamus, pituitary gland, adrenal glands, gonads, (i.e., testes and ovaries), thyroid gland, parathyroid glands, and pancreas (see figure 1). The term “endocrine” implies that in response to specific stimuli, the products of those glands are released into the bloodstream. The hormones then are carried via the blood to their target cells. Some hormones have only a few specific target cells, whereas other hormones affect numerous cell types throughout the body. The target cells for each hormone are characterized by the presence of certain receptors for the hormone that are located either on the cell surface or inside the cell. The interaction between the hormone and its receptor triggers a cascade of biochemical reactions in the target cell that eventually modify the cell’s function or activity.
There are three general classes of hormones (Table 1):
1. Proteins and polypeptides, including hormones secreted by the anterior and posterior pituitary gland, the pancreas (insulin and glucagon), the parathyroid gland (parathyroid hormone), and many others.
2. Steroids, secreted by the adrenal cortex (cortisol and aldosterone), the ovaries (estrogen and progesterone), the testes (testosterone), and the placenta (estrogen and progesterone).
3. Derivatives of the amino acid tyrosine, secreted by the thyroid (thyroxine and triiodothyronine) and the adrenal medullae (epinephrine and norepinephrine).
Figure 1. Endocrine gland that can produce hormones
Table 1. Classification of hormones depending upon chemical nature.
|Steroids||Proteins||Derivatives of tyrosine|
Growth hormone (GH)
Thyroid-stimulating hormone (TSH)
Adrenocorticotropic hormone (ACTH)
Follicle-stimulating hormone (FSH)
Luteinizing hormone (LH)
Antidiuretic hormone (ADH)
Human chorionic gonadotropin (HCG)
Human chorionic somatomammotropin
Those hormone classes differ in their general molecular structures. As a result of the structural differences, their mechanisms of action also differ.
Polypeptide and protein hormones are chains of amino acids of various lengths. These hormones are found primarily in the hypothalamus, pituitary gland, and pancreas. In some instances, they are derived from inactive precursors, or pro-hormones, which can be cleaved into one or more active hormones. Because of their chemical structure, the polypeptide and protein hormones cannot enter cells. Instead, they interact with receptors on the cell surface. The interaction initiates biochemical changes in either the cell’s membrane or interior, eventually modifying the cell’s activity or function.
Steroids, which are produced by the gonads and part of the adrenal gland (i.e., the adrenal cortex), have a molecular structure similar to that of cholesterol. The molecules can enter their target cells and interact with receptors in the cytoplasm or in the cell nucleus. The hormone receptor complexes then bind to certain regions of the DNA, thereby regulating the activity of specific hormone-responsive genes.
Amino acid derivatives are modified versions of some of the building blocks of proteins. The thyroid gland and another region of the adrenal glands (i.e., the adrenal medulla) produce this type of hormone. Like steroids, amino acid derivatives can enter the cell, where they interact with receptor proteins that are already associated with specific DNA regions. The interaction modifies the activity of the affected genes.