Endocrine System Facts

The glands of the endocrine system are ductless, which means the hormones secreted by these glands are discharged directly into the bloodstream.

The endocrine system consists of a collection of small glands that regulate a number of vital functions of our body. All these glands coordinate with each other exceptionally well in order to regulate various life processes.

To learn more about the endocrine system, let us have a look at the glands that form a part of this system, and how each one of them functions.

► The hypothalamus is a gland located above the brain stem, adjacent to the pituitary, and is called the "master switchboard", as it is the main control center of the autonomous nervous system.

► It sends messages to the pituitary gland, which in turn secretes hormones to regulate the functions of the body.

► Whenever any part of the body is subjected to stimuli such as heat, cold, pain, etc, it triggers the release of the corticotropin-releasing hormone (CRH), which is also known as the corticotropin-releasing factor (CRF), from the hypothalamus.

The CRH stimulates the secretion of the adrenocorticotropic hormone (ACTH) from the anterior pituitary, which in turn stimulates the secretion of corticosteroids from the adrenal glands.

► An important function of the hypothalamus is to regulate body temperature, hunger, and thirst. It also regulates the functioning of all the internal organs.

► It serves as a crucial link between the endocrine system and the nervous system.

► The shape and size of the pituitary gland is quite similar to that of a pea, and it is located just below the hypothalamus, at the base of the brain.

► It is the most important endocrine gland in the body, and is also referred to as the "master gland", as its secretions regulate most other endocrine glands in the body.

► The pituitary gland is also known as the hypophysis.

► It is connected to the hypothalamus by a short stalk.

► It has three lobes, namely, the anterior lobe, the intermediate lobe, and the posterior lobe.

► Here's a list of the hormones secreted by the three lobes of the pituitary, along with the function performed by each.

• Growth hormone (HGH): Produced by the anterior lobe of the pituitary, this hormone is also known as somatotropin, and regulates the growth of the body.

• Antidiuretic hormone (ADH): Produced by the posterior lobe of the pituitary, its function is to regulate water retention in the body by controlling the reabsorption of water by the kidneys. It is also known as vasopressin.

• Adrenocorticotropic hormone (ACTH): Produced by the anterior lobe of the pituitary, the function of this hormone is to stimulate the release of corticosteroids by the adrenal glands, in situations of physiological stress. It is also known as corticotropin.

• Thyroid stimulating hormone (TSH): Produced by the anterior lobe of the pituitary gland, its function is to stimulate the thyroid glands to secrete thyroxin. It is also known as thyrotropin.

• Follicle-stimulating hormone (FSH) and Luteinizing hormone (LH): Both these hormones are secreted by the gonadotrophs of the anterior lobe. FSH regulates the development and growth of the reproductive processes.

In females, an increase in the levels of FSH causes ovulation. LH, also known as lutropin, regulates the development of the corpus luteum in females. In males, it regulates the production of testosterone by the Leydig cells.

• Melanocyte-stimulating hormone (MSH): Secreted by the interior lobe of the pituitary, the function of this hormone is the production of the pigmented cells called melanin.

► The pineal gland is also known as the pineal body or the "third eye".

► It is a small endocrine gland which is located in the brain, and secretes the hormone melatonin. The function of melatonin is to regulate sleep patterns.

► The pineal gland is shaped like a pine cone.

► The thyroid gland is positioned at the front side of the lower neck, very close to the larynx. It is partially surrounded by the trachea.

► The shape of this gland is like a butterfly or a bow tie.

► It produces essential hormones like thyroxine (T4), triiodothyronine (T3), and calcitonin.

► The thyroid hormones (thyroxine and triiodothyronine) play a key role in body growth, brain development, and development of muscles and bones.

► The function of calcitonin is to maintain the levels of calcium in the body.

► The thyroid gland has a right lobe and a left lobe, and they are connected to each other by an isthmus.

► The thyroid gland secretes thyroxin after it is stimulated by the thyroid stimulating hormone (TSH) secreted by the anterior pituitary gland.

► The minerals that are essential for the proper functioning of the thyroid, are iodine, manganese, magnesium, and zinc.

► Parathyroid glands are glands that are located in the anterior part of the thyroid gland, and are four in number. These glands secrete the hormone parathyroid (PTH), which plays a key role in vitamin D synthesis.

► The thymus gland is located in the upper part of the thoracic cavity.

► It plays a key role in strengthening the immune system in children.

► It secretes thymosins, which are hormones that stimulate the production of antibodies.

► It continues to grow till a person attains puberty, after which it begins to shrink.

► It is also the site for the synthesis of T-lymphocytes, which are white blood cells associated with the production of antibodies.

► The pancreas is located just below the stomach.

► It is a double gland which functions as an endocrine as well as an exocrine gland. It performs both, digestive and endocrine functions, and is made up of two different kinds of tissues.

► The endocrine part of the pancreas is termed as the islets of Langerhans, and it secretes the hormones insulin and glucagon. The function of these hormones is to regulate the blood glucose level. While glucagon is secreted by the alpha cells of the islets of Langerhans, insulin is secreted by the beta cells.

► If the pancreas does not produce enough insulin, then the sugar level in blood rises, which leads to diabetes.

► The adrenal glands are two cap-shaped glands located one above each kidney.

► Each adrenal gland has two parts, the outer part is known as the adrenal cortex, and the inner part is known as the adrenal medulla.

► The adrenal cortex secretes the hormones aldosterone and cortisol. The hormones secreted by the adrenal medulla are epinephrine and norepinephrine.

► The hormones secreted by the adrenal glands help the body cope with and respond to stress, and also maintain the salt and water balance.

► The reproductive glands consist of the testes in males and the ovaries in females. These glands secrete the sex hormones.

► The testes are located in the scrotum of males, while the ovaries are located in the pelvic region of the females.

► The testes secrete the male hormone testosterone which regulates the development of secondary sexual characteristics, which include increased stature, growth of facial and body hair, increased strength and muscle mass, deepening of voice due to enlargement of the larynx or voice box, lower body fat percentage, etc.

Testosterone is also essential for sperm production during the process of spermatogenesis.

► The ovaries secrete the female hormones estrogen and progesterone. Estrogen is essential for the formation of the ovum (egg) during the process of oogenesis. Estrogen also prepares the uterus for the implantation of the fertilized egg. Progesterone is the hormone that regulates the menstrual cycle in females.

Improper functioning of any of these glands can lead to either too much or too little production of the essential hormones, which can have adverse effects on our overall health. In addition to the endocrine glands listed above, there are a few other organs that perform endocrine functions. These are the liver, stomach, kidney, placenta, and the uterus.