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Endocrine System and Hormone Regulation: Maintaining Internal Balance

Writer's picture: biologicalfervorbiologicalfervor
Mar 21, 20246 min read

Written by: Minahil Mumtaz 


Figure 1. Endocrine System in Humans


Hormones

“Hormones are chemicals synthesized and produced by the specialized glands to control and regulate the activity of certain cells and organs."

These signals tell your body what to do and when to do it. Hormones are essential for life and your health.

Types of Hormones

To regulate various functions, different types of hormones are produced in the body. They are classified as follows:

  • Peptide Hormones

  • Steroid Hormones

Peptide Hormones

Peptide hormones are composed of amino acids and are soluble in water. Peptide hormones are unable to pass through the cell membrane as they contain a phospholipid bilayer that stops any fat-insoluble molecules from diffusing into the cell. Insulin is an important peptide hormone produced by the pancreas.

Steroid Hormones

Unlike peptide hormones, steroid hormones are fat-soluble and can pass through a cell membrane. Sex hormones such as testosterone, estrogen, and progesterone are examples of steroid hormones.


What is the Endocrine System?

The Endocrine System is a messenger system in an individual composed of internal glands that make hormones. The endocrine system influences almost every cell, organ, and function of our bodies. It's quite similar to the nervous system as it plays a vital role in controlling, regulating, and maintaining the body functions. But unlike the nervous system, it uses hormones.

Function of Endocrine System

The main function of the endocrine system is to release hormones into the blood while continuously monitoring the levels. Hormones deliver their messages by locking into the cells they target, so they can transmit the message. Some examples include:

  • Metabolism

  • Homeostasis

  • Sexual functions

  • Reproduction

  • Growth & Development

  • Mood & Sleep-Wake Cycle

Anatomy of the Endocrine System

The endocrine system is made up of seven different glands:

  • Hypothalamus 

  • Pituitary Gland

  • Thyroid Gland

  • Parathyroid Gland

  • Adrenal Gland

  • Pancreas 

  • Pineal Gland

  • The Ovaries

  • The Testes


All these glands work together to produce and manage the hormones of the body. These are described below:


Hypothalamus

The hypothalamus is located in the center of the brain. It makes hormones that increase or decrease the release of the hormones made in the pituitary gland. It also makes hormones that help to control water balance, sleep, temperature, appetite, thirst, and blood pressure.  It controls the body temperature, regulates emotions and moods, and allows the production of hormones.

Figure 2.  Hypothalamus in the Brain

Pituitary Gland

The pituitary gland is located at the base of the brain and is about the size of a pea. It is the master gland in the endocrine system. It regulates the amounts of hormones made by the thyroid gland, adrenal gland, and testes or ovaries. It also makes the hormones prolactin, vasopressin, and growth hormones.

Figure 3. Pituitary Gland

Thyroid and Parathyroid

The thyroid gland and parathyroid glands are located in front of the neck, below the larynx (voice box). The thyroid plays an important role in the body's growth and development, as well as metabolism. Both the thyroid and parathyroid glands also play a role in controlling the level of calcium in the body.

Figure 4. Thyroid and Parathyroid Glands 

Adrenal Gland

The adrenal glands are located on top of each kidney. The adrenal glands make hormones that help the body deal with stress and illness. The hormones made by the adrenal gland also maintain blood pressure and blood glucose and play a role in sexual development.

Figure 5. Adrenal Gland

Pancreas

The pancreas is located behind the stomach. It plays a role in digesting food, but it also makes hormones. The pancreas makes insulin, which is important for blood sugar control.

Figure 6. Pancreas

Pineal Gland

The main function of the pineal gland is to receive information about the state of the light-dark cycle from the environment and convey this information by the production and secretion of the hormone melatonin.

Figure 7. Pineal Gland

Ovaries  

A female's ovaries are located on both sides of the uterus, below the opening of the fallopian tubes (which extend from the uterus to the ovaries). In addition to containing the egg cells necessary for reproduction, the ovaries also produce the hormones estrogen and progesterone. These hormones regulate the menstrual cycle.
Figure 8. The Ovaries

Testes

A male's testes are located in the scrotum. The testes secrete the male sex hormone known as testosterone. It also produces sperm.

Figure 9. The Testes


Important Hormones and Their Functions

Here, some most important hormones of the body are described along with their functions.

  • Cortisol

Cortisol is a steroid hormone that is produced by your 2 adrenal glands. When you are stressed, increased cortisol is released into your bloodstream. Having the right cortisol balance is essential for your health. Cortisol is also needed for the ‘fight or flight’ response, which is your healthy, natural response to perceived threats.

Figure 10. Structure of Cortisol

  • Estrogen

Estrogens are a group of hormones that play an important role in normal sexual and reproductive development in women. They are also sex hormones. In addition to regulating the menstrual cycle, estrogen affects the reproductive tract, the urinary tract, the heart and blood vessels, bones, breasts, skin, hair, mucous membranes, pelvic muscles, and the brain. When estrogen level rises, the secondary sexual characteristics, such as pubic and armpit hair, also start to grow.

Figure 11. Structure of Estrogen

  • Testosterone

Testosterone is the primary male hormone responsible for regulating sex differentiation, producing male sex characteristics, spermatogenesis, and fertility.

Figure 12. Structure of Testosterone

  • Insulin

Insulin is a naturally occurring hormone your pancreas makes that's essential for allowing your body to use sugar (glucose) for energy. If your pancreas doesn't make enough insulin or your body doesn't use insulin properly, it leads to high blood sugar levels (hyperglycemia). This results in diabetes.

Figure 13. Structure of Insulin

  • Melatonin

Melatonin is a hormone that your brain produces in response to darkness. It helps with the timing of your circadian rhythms (24-hour internal clock) and with sleep. Being exposed to light at night can block melatonin production. Research suggests that melatonin plays other important roles in the body beyond sleep.

Figure 14. Structure of Melatonin

  • Thyroid Hormone

The thyroid hormone is well known for controlling metabolism, growth, and many other bodily functions. The thyroid gland, anterior pituitary gland, and hypothalamus comprise a self-regulatory circuit called the hypothalamic-pituitary-thyroid axis.

Figure 15. Structure of Thyroid Hormone

  • Growth Hormone

Growth hormone is produced by our brain's pituitary gland and governs our height, bone length, and muscle growth. Some people abuse synthetic growth hormone in the mistaken belief it will help them increase muscle size and strength.

Figure 16. Structure of Growth Hormone

  • Progesterone

Progesterone plays an important role in your menstrual cycle and pregnancy. Progesterone creates a healthy uterine lining to support a fertilized egg, embryo, and fetus. If progesterone levels are too low during pregnancy, it could cause complications such as bleeding or miscarriage.

Figure 17. Structure of Progesterone

  • Adrenaline

Adrenaline (epinephrine) is a hormone your adrenal glands make to help you prepare for stressful or dangerous situations. Adrenaline rush is the name for the quick release of adrenaline into your bloodstream. This gets your body ready for a “fight or flight” response.

Figure 18. Structure of Adrenaline

  • Adrenocorticotropic Hormone

Adrenocorticotropic hormone (ACTH) is produced by the pituitary gland. Its key function is to stimulate the production and release of cortisol from the cortex (outer part) of the adrenal gland.

Figure 19. Structure of Adrenocorticotropic Hormone

  • Oxytocin

The two main physical functions of oxytocin are to stimulate uterine contractions in labor and childbirth and to stimulate contractions of breast tissue to aid in lactation after childbirth.

Figure 20. Structure of Oxytocin

  • Prolactin

Prolactin contributes to hundreds of physiologic functions, but the two primary responsibilities are milk production and the development of mammary glands within breast tissues. Prolactin promotes the growth of mammary alveoli, which are the components of the mammary gland, where the actual production of milk occurs.

Figure 21. Structure of Prolactin






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