The Endocrine System: The Body's Chemical Messangers

 Hey! Today, I'm gonna be talking about the most underrated and unobtrusive system inside the body. It's functions are exceedingly vital for the human body to function. This system is what keeps us alive, makes us breathe and makes our heart beat. I am talking about The Endocrine System. 

What are Hormones?

The Body's Chemical Messengers are known as Hormones. They are small molecules which carry out various actions in our body, ranging from controlling our blood pressure, to controlling our sugar levels, to making sperm, to making us happy, anxious, excited etc. They are released by endocrine glands. The 4 feel good hormones which make us feel happy, are Oxytocin, Serotonin, Endorphins and Dopamine. 

Let's give you a brief about the organs which make up this system, Glands!

What are Glands?

Glands are like organs which make and secrete substances such as hormones, digestive juices, enzymes etc. There are 2 types of glands in the human body:-

1. Exocrine glands- They are called glands with ducts as they release a hormone through ducts, which are small openings, directly onto the skin, or the epithelial surface. Their products include sweat, tears, saliva and milk. Ex- The eyes release tears, the skin produces sweat and oil,  the mouth produces saliva, all through exocrine glands.

2. Endocrine Glands- They are called ductless glands, as they release their hormones directly into the bloodstream. One important thing to remember is that their hormones travel through the blood, onto the target sites, where they act. Meaning, the hormones do not show any action, where they are released, they act specifically on the target sites. Ex- The pituitary gland releases its hormone, into the bloodstream, which travels to the Thyroid gland and activates the gland to release its hormone

Endocrine Anatomy

 All the important glands in the human body are as follows:-

• Hypothalamus- The Master Gland of the Body. Located just above the Brain stem. 
• The Pituitary Gland- The most important gland of the body. Located just below the Hypothalamus. There are 2 parts of this gland, the anterior and posterior pituitary glands. 
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• The Pineal Gland- The least understood and the latest discovered gland in the body, also has a neurological function. Located in the mid-line of the brain. 
• The Thyroid Gland- Located in the throat region, the most commonly well-known gland. 
• 2 Pairs of Parathyroid Glands- One pair known as The Inferior Parathyroid glands and the other pair known as the Superior Parathyroid glands. All in all, there are 4 parathyroid glands, embedded in the back of the thyroid gland. 
• Thymus Gland- A gland which also has an immune function, which is creating white blood cells. The only gland in the body, which starts to shrink when humans reach puberty and it becomes non-functional in adults. Located in between the lungs, and behind the sternum (breastbone). 
• Pancreas- A dual-purpose gland, as it is also an organ. It also has an exocrine function as it also has a pancreatic duct.  Located behind the stomach in the upper left abdomen. 
• A Pair of Adrenal Glands- They secrete one of the most important hormones, and produce the most diverse quantity of hormones. They are made up of the Adrenal Cortex (outer part) and the Adrenal Medulla (inner part). 2 Adrenal Glands are located on top of the 2 kidneys. 
• Ovaries (In Females)- Also an organ, a pair of ovaries are located in the fallopian tube on the left and right sides of the abdomen. 
• Testes (In Males)- The testes or testicles in males are also an organ. Located inside the scrotum, behind the penis. 

Both the Ovaries and Testes produce sex hormones.

All The Important Hormones in the Body

All the important Hormones in the body, and the gland by which they are secreted are as follows:-

• Hormones such as Somatostatin and Thyrotropin-releasing hormone are the main hormones released by the Hypothalamus.
• Follicle-stimulating Hormone or FSH, Thyroid-Stimulating Hormone or TSH, Somatotropin (Growth Hormone) and Prolactin are some of the main hormones released by the Pituitary Gland.
• Melatonin is secreted by the Pineal gland.
• Thyroxine is the main hormone secreted by the Thyroid Gland.
• Parathormone (Parathyroid Hormone) and Calcitonin are the main hormone secreted by the Parathyroid Glands.
• Thymosin and Thymulin are the main hormones secreted by the Thymus gland.
• Insulin and Glucagon are the main hormones secreted by the Pancreas.
• The Adrenal Cortex secretes Cortisol (Mineralocorticoid), Aldosterone (Glucocorticoid) and Androgens. The Adrenal Medulla secretes Epinephrine (Adrenaline), Norepinephrine (Noradrenaline) and Gonadocorticoids.
• The Ovaries in females secrete Oestrogen and Progesterone known as Sex Hormones.
• The Testes in males secrete Testosterone known as Sex hormone.

One important thing to remember is that even testes produce progesterone and oestrogen, and even the ovaries produce testosterone, just in very small quantities.

Functions of The Important Hormones 

The functions' of all the hormones listed above are as follows:-

• Somatostatin affects memory formation in the CNS, and also prevents the secretion of too much of any hormone.
• Thyrotropin-Releasing Hormone stimulates the release of the TSH by the anterior pituitary gland.
• FSH stimulates the follicles of the ovary to grow and prepare the eggs for ovulation. The content of this hormone is highest on the days of ovulation in female.
• TSH stimulates the Thyroid to release its hormone, Thyroxine.
• Somatotropin or Growth Hormone acts on the body as a whole, to promote growth in all parts, such as the bones.
• Prolactin stimulates the development of mammary glands within breast tissues.
• Melatonin makes us asleep and keeps our circadian rhythm (24-hour sleep-wake cycle) in check.
• Thyroxine plays a vital role in metabolism, heart health, muscle health and providing the body with Iodine.
• Parathormone regulates Calcium Levels in the Blood.
• Calcitonin blocks the activity of Osteoclasts.
• Thymosin stimulates the growth of T-cells.
• Thymulin enhances the activity of Anti-inflammatory cytokines and blocks the activity of Pro-inflammatory Cytokines.
• Insulin decreases sugar level in the blood when its too high.
• Glucagon increases sugar level in the blood when its too low.
• Cortisol make your body respond to stress, maintains blood pressure, increases body's metabolism and reduces inflammation.
• Aldosterone regulates levels of sodium and potassium in the blood.
• Androgens stimulate the production of sperm in the testes.
• Epinephrine (Adrenaline) makes you heart beat faster and your lungs breathe more efficiently. It causes your blood vessels to send more blood to your brain and muscles, increases your blood pressure, makes your brain more alert, and raises blood sugar levels to give you energy. Your pupils grow larger and you sweat. It does this in times of stress, or when something dangerous is happening. It gets you ready for action. It is also known as the "Fight or Flight" Hormone.
• Norepinephrine (Noradrenaline) makes your heat beat slower, decreases your blood pressure, decreases the blood sugar level and decreases the activity of the sweat glands. It also helps you stay focused and alert. It is basically the opposite of epinephrine.
• Gonadocorticoids affect distribution of body hair in female.
• Oestrogen plays a role in breast health and stimulates the release of an ovum or egg during ovulation.
• Progesterone thickens the lining of the uterus to prepare it for pregnancy.
• Testosterone regulates sex drive, fat distribution, muscle mass and strength.

Hormones which are secreted by Organs

Some organs secrete hormones too, and they do this to keep their own organic functions in check.

Heart

Atrial Natriuretic Peptide (ANP), more commonly known as Atriopeptin is a hormone secreted by the right atrium in response to hypertension. Brain Natriuretic Peptide (BNP) is secreted when your heart is working harder than normal to pump blood and it tells your blood vessels to get wider.

Kidney

Erythropoietin is secreted by the juxtaglomerular cells of the kidney to maintain a healthy amount of red blood cells. Anti-Diuretic Hormone or Vasopressin released by the kidney tubules controls the amount of water removed from kidneys.

Leptin is a hormone that the adipose tissue releases to maintain our weight on a long-term basis. It does this by regulating hunger and providing the sensation of fullness (satiety reflex).

Melanocyte-Stimulating Hormone or MSH stimulates the production of Melanin in the skin, which is a hormone which makes our skin colour darker.

How the system functions?

The hypothalamus releases thyrotropin-releasing hormone which tells the pituitary gland to release Thyroid-Stimulating Hormone or TSH which in turn, tells the thyroid gland to secrete thyroxine, the hormone travels through the bloodstream to its target site and then finally does it's job. 

 

Hormonal Disorders

• Hyperthyroidism and Hypothyroidism- In hyperthyroidism, the thyroxine hormone is produced too much by the thyroid gland, which results in the metabolic function of the body speeding up, resulting in Hyperactivity. A lot of Hyperthyroidism cases are because of Graves' Disease. Hypothyroidism is the opposite, so the body gradually slows down, resulting in tiredness without doing anything. 
• Diabetes (Both Type 1 and Type 2)- Diabetes Type 1 is an autoimmune disorder, in which the beta cells in the pancreas are destroyed, so the pancreas either produces too little insulin or it doesn't produce insulin at all. Because of which blood sugar levels go too high in the body. In Diabetes Type 2, the pancreas secretes insulin but the cells are unable to respond to it. Because of which the blood level again goes too high in the body. Symptoms for both of them are  are Thirst, Fatigue, Frequent Urination, Weight Loss, Blurred vision etc. 

I hope that by now, all of you know how much of an important role Hormones play in our Bodies. The Endocrine System is complex and we are still learning about it. 

Fun Fact! 

The Doctor associated with the stream of this system, is known as an Endocrinologist.

Regards,

Deeparsh Bhanot