What is the endocrine system?
The endocrine system is a network of hormones and glands that produce, store, and secrete hormones. Hormones are chemical messengers created by the body. They transfer information from one set of cells to another to coordinate the functions of different parts of the body. These hormones regulate the body’s growth and development, metabolism (the physical and chemical processes of the body), sexual development and function, and it plays a big role in how systems work with each other to regulate your body’s healthy development and function throughout life.
The endocrine system is regulated by feedback in much the same way that a thermostat regulates the temperature in a room, and hormones travel throughout the body and act as chemical messengers. The endocrine system regulates adjustments through slower internal processes, using hormones as messengers, and the systems work together to maintain the proper functioning of the body through its entire life cycle. The endocrine system secretes hormones in response to environmental stimuli and to orchestrate developmental and reproductive changes. These adjustments brought on by the endocrine system are biochemical, which changes the cell’s internal and external chemistry to cause long-term change in the body.
The major glands of the endocrine system are the hypothalamus, pituitary, thyroid, parathyroids, adrenals, pineal body, and the reproductive organs (ovaries and testes). The pancreas is also a part of this system; it has a role in hormone production as well as in digestion.
Hypothalamus
The hypothalamus is a part of the brain (located in the lower central part) that has a vital role in controlling many bodily functions including the release of hormones from the pituitary gland, and it is important in the regulation of satiety, metabolism, and body temperature.
Pituitary Gland
The pituitary gland is a pea-sized endocrine gland located is situated in a bony hollow, just behind the bridge of your nose (at the base of the brain). It is often considered the most important part of the endocrine system because it produces hormones that is important in controlling growth and development and the functioning of other endocrine glands.
When the pituitary gland does not produce one or more of its hormones or not enough of them, it is called hypopituitarism.
The pituitary gland’s frontal (anterior) lobe produces the following hormones (which are regulated by the hypothalamus):
- Growth hormone: to stimulates the growth of bone and tissue
- Thyroid-stimulating hormone (TSH): it stimulates the thyroid gland to produce thyroid hormones. (A lack of thyroid hormones is called hypothyroidism)
- Adrenocorticotropin hormone (ACTH): it stimulates the adrenal gland to produce several related steroid hormones
- Luteinizing hormone (LH) and follicle-stimulating hormone (FSH): it is hormones that control sexual function and production of the sex steroids, estrogen and progesterone in females or testosterone in males
- Prolactin: it is a hormone that stimulates milk production in females
The back (posterior) lobe produces the following hormones (which are not regulated by the hypothalamus, and stored in the pituitary gland):
- Antidiuretic hormone (vasopressin): it controls water loss by the kidneys
- Oxytocin: it contracts the uterus during childbirth and stimulates milk production
Thyroid Gland
The thyroid gland is a small organ situated in the lower front part of the neck. It produces thyroid hormones that regulate the body’s metabolism it plays a role in bone growth and development of the brain and nervous system in children, and helps to maintain normal blood pressure, heart rate, digestion, muscle tone, and reproductive functions.
The pituitary gland controls the release of thyroid hormones.
Symptoms of an overactive thyroid (hyperthyroidism) can include anxiety, irritability and nervousness, having trouble sleeping, losing weight, having an enlarged thyroid gland, having muscle weakness and tremors, experiencing irregular menstrual periods or having your menstrual cycle stop, feeling sensitive to heat, and having vision problems or eye irritation.
Symptoms of an underactive thyroid (hypothyroidism) can include feeling tired (fatigue), gaining weight., experiencing forgetfulness, having frequent and heavy menstrual periods, having dry and coarse hair, having a hoarse voice, and experiencing an intolerance to cold temperatures.
Parathyroid Glands
The parathyroid glands are two pairs of small glands embedded in the surface of the thyroid gland, one pair on each side. They release parathyroid hormone, which are important in tightly controlling calcium levels in the bloodstream and bone metabolism.
If this gland makes too much parathyroid hormones, patients may develop a blood level of calcium that is too high (hypercalcaemia), which may include symptoms of increased thirst, increased urine production, abdominal pain, constipation, generalised aches and pains, changes in mood.
Adrenal Glands
The two adrenal glands are triangular-shaped glands located on top of each kidney. The adrenal glands are made up of two parts. The outer part of the adrenal glands named the adrenal cortex produces hormones called corticosteroids, which regulate the body’s metabolism, the balance of salt and water in the body, the immune system, and sexual function. The inner part of the adrenal glands named the adrenal medulla produces hormones called catecholamines (for example, adrenaline). These hormones help the body cope with physical and emotional stress by increasing the heart rate and blood pressure.
Pancreas
The pancreas is a long, flat gland that sits tucked behind the stomach in the upper abdomen.
The pancreas produces enzymes that help digestion and hormones that help regulate the way your body processes sugar (glucose).
What are endocrine disruptors?
Endocrine-disrupting chemicals (EDCs) are substances in the environment (air, soil, or water supply), food sources, personal care products, and manufactured products that interfere with the normal function of your body’s endocrine system. Many endocrine disruptors are found in everyday products, including some plastic bottles and containers, liners of metal food cans, detergents, flame retardants, food, toys, cosmetics, and pesticides.
Disruption of the endocrine system can occur in various ways. Many chemicals (both natural and man-made) mimic a natural hormone, fooling the body into over-responding to the stimulus (e.g., a growth hormone that results in increased muscle mass), or responding at inappropriate times (e.g., producing insulin when it is not needed). Other endocrine disruptors block the effects of a hormone from certain receptors (e.g., growth hormones required for normal development). Still others directly stimulate or inhibit the endocrine system and cause overproduction or underproduction of hormones (e.g., an over or underactive thyroid).
Certain drugs are used to intentionally cause some of these effects, such as birth control pills. In many situations involving environmental chemicals, however, an endocrine effect is not desirable.
Synthetic chemicals in products like plastics and fragrances can mimic hormones and interfere with or disrupt the delicate endocrine dance, and any system in the body controlled by hormones can be derailed by hormone disruptors. Specifically, it may be associated with the development of learning disabilities, severe attention deficit disorder, cognitive and brain development problems, deformations of the body (including limbs), interference with reproduction, metabolism and obesity, disturbances in the immune and nervous system function, breast cancer, prostate cancer, thyroid and other cancers, and sexual development problems.
It should be noted that researched showed that endocrine disrupting chemicals causes adverse effects in animals, but limited scientific information exists on potential health problems in humans. This is because people are typically exposed to multiple endocrine disruptors at the same time and assessing public health effects is therefore difficult. However, the relationship of human diseases of the endocrine system and exposure to environmental contaminants is poorly understood and scientifically controversial. Nevertheless, there is little doubt that small disturbances in the endocrine function (particularly during certain highly sensitive stages of the life cycle, e.g., development, pregnancy, lactation) can lead to profound and lasting effects.
How do people encounter endocrine-disrupting chemicals?
People may be exposed to endocrine disruptors through food and beverages consumed, pesticides applied, and cosmetics used. Since EDCs come from many different sources, people are exposed in several ways and contact with these chemicals may occur through the air we breathe, the food we eat, and the water we drink. It can also enter the body through the skin.
Even low doses of endocrine-disrupting chemicals may be unsafe. The body’s normal endocrine functioning involves very small changes in hormone levels, yet we know even these small changes can cause significant developmental and biological effects. This observation leads scientists to think that endocrine-disrupting chemical exposures, even at low amounts, can alter the body’s sensitive systems and lead to health problems.
What are some common endocrine disruptors?
See further info on the specific Endocrine Disruptors.