What are hormones?
There are two ways that one region of our body can communicate with another. The first is by way of nerve impulses and the second is by way of hormones. Hormones are produced by specific organs (glands) in the body including the pituitary gland, parathyroid gland, thyroid gland, hypothalamus, pancreas, stomach, small intestine, adrenal glands, placenta, and gonads (ovaries and testicles) (see Hormone FunctionTable). Hormones are released into our blood and circulate throughout our body. As they circulate they can interact with specific cells of a specific tissue and elicit a response within those cells.
Which types of tissue will Only cells that have a specific receptor for a hormone will respond to a circulating hormone. This is an extremely accurate operation. Some hormones may have receptors on cells of only one kind of tissue in our body, while other hormones may have receptors on cells of most tissues in our body. For example, the hormone prolactin stimulates milk production in female breasts. Therefore, the cells associated with the milk-producing mammary glands will have receptors for prolactin, while most other cells in our body will not have prolactin receptors and will not be affected by prolactin. Thyroid hormone and insulin receptors, on the other hand, will be found on the cells of many kinds of tissues in our body.
Organ of Origin |
Hormone |
Primary Action |
Pituitary Gland |
Growth Hormone (GH) |
Increases growth of most tissue; increases protein synthesis and fat use for energy |
Pituitary Gland |
Prolactin |
Increases milk production in female mammary glands |
Pituitary Gland |
Antidiuretic Hormone (ADH) |
Decreases water loss by our kidneys by increasing water reabsorption by our nephrons |
Thyroid Gland |
Thyroid Hormone (T3/T4) |
Increases rate of metabolism in our cells; normal growth |
Thyroid Gland |
Calcitonin |
Decreases blood calcium levels by increasing kidney loss and decreasing absorption in our gut |
Parathyroid Gland |
Parathyroid Hormone (PTH) |
Increases blood calcium levels by decreasing urinary losses and increasing absorption in the gut |
Adrenal Gland |
Aldosterone |
Increases sodium reabsorption in kidneys (decreases urinary loss of sodium) |
Adrenal Gland |
Cortisol |
Increases glucose production in the liver and release into blood; stimulates muscle protein breakdown, promotes inflammation; increases fat release from fat cells |
Adrenal Gland |
Epinephrine (Adrenalin) |
Increases heart rate and stroke; increases glucose production in liver and release into our blood, increases fat release from fat cells |
Pancreas |
Insulin |
Increase glucose uptake into muscle and fat tissue; increases storage of glucose as glycogen; decreases fat release from fat cells and increases fat production; increases protein production |
Pancreas |
Glucagon |
Increases fat release from fat cells; increases glucose production in the liver and release into blood |
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