To Endocrinology and Beyond!

Silly Hormones!

The blogger's grade school yearbook.

Image credit: JERJ

I was cleaning my room the other day when my grade school yearbook caught my attention. I don't quite remember when was the last time I opened it as it was under a pile of books and layers of dust that may have accumulated over the past years. As I open it, I was shocked at how different I looked before. I was very thin and looked really young. Some of my elementary friends, who I still keep in touch with today, looked different too! Pardon me as I use a very cliched quote, but "change, indeed, is inevitable". The human body is the very epitome of how nothing in this world is permanent. 

I asked myself, What is the cause of these changes? Or rather, What system in the body is responsible for these physiologic changes that every human, especially those in their adolescent years, experience?

In addition to these questions, I have also encroached on the subject of diseases like diabetes mellitus (DM) and dwarfism. Is it possible that the reasons behind growth spurts and adolescent changes are also the ones responsible for these diseases? And so I made some research to help enlighten myself and others who have the same questions in mind.

The Endocrine and The Nervous System

I have found out that there are two particular systems in our body responsible for the physiologic changes that we experience. These two systems are the Nervous and the Endocrine System. They do not just control some of the biological functions of our body but they also influence behavior. 


As a Clinical Chemistry student, I have decided to focus more on the Endocrine System. Endocrinology is the field of medical science that deals with the study of the different glands that make up the endocrine system as well as with the hormones that they secrete which play a role in maintaining the body's normal biologic and physiologic functions.

Pass Me the Message

The Endocrine system consists of a lot of ductless glands. These different glands, which I will be discussing with more depth later, release hormones which are active chemical regulators that circulate in the bloodstream. These hormones regulate the biologic functioning and growth of our bodies by interacting with the specific receptors present on the cells of all our organs. There are also some hormones that stimulate nearby cells. They are able to do this function by flowing through the extracellular fluid of our bodies. 


You may ask yourself, what are the differences between the endocrine and the nervous system? I do have my answer for that. If the endocrine system is a chemical network that transmits messages to all the organs of our body via the bloodstream, the nervous system acts only locally. In response to nerve impulses, the system releases neurotransmitters. The sites of action are close to where the neurotransmitters are released (synapse).

The Glands of the Chemical Communication Network

The glands of the chemical communication network.

IC: http://www.emc.maricopa.edu/faculty/farabee/biobk/endocrorgs.gif

Let us now talk about the glands that make up the endocrine system. For ease of understanding, I decided to arrange the glands in the form of bullets with clear and concise descriptions for each.

• Hypothalamus

IC: http://www.daviddarling.info/encyclopedia/P/pituitary_gland.html

• this is the gland that is responsible for the internal homeostasis (balance) of the body
• produces at least 9 different hormones
• found below the thalamus
• serves as the major link between the endocrine and the nervous systems

• Pituitary Gland

IC: http://www.pennmedicine.org/health_info/body_guide/reftext/images/PituitaryGland.jpg

• also known as hypophysis
• called the "master gland" but in turn serves the hypothalamus
• secretes 7 different hormones
• hormones secreted by this organ control growth
• the rest of the endocrine system is controlled and regulated by this organ

• Thyroid Gland

IC: http://www.pyroenergen.com/articles08/images/thyroid-gland.jpg

• gland that is butterfly-shaped
• mostly made up of thyroid follicles
• the hormones tetraiodothyronine (T4) and triiodothyronine (T3) are produced by this gland
• parafollicular cells produce calcitonin (calcium homeostasis)

• Parathyroid Glands

IC: http://www.pauerhome.com/ryan/endocrine_system/pictures/parathyroid_gland_diagram_1.jpg

• small, round masses of tissue weighing 40 mg each
• the epithelial cells contained in this glands are the chief cells and the oxyphil cells
• the parathyroid hormone, also known as PTH and parathormone, is produced by the chief/principal cells

• Adrenal Glands

IC: http://www.daviddarling.info/encyclopedia/A/adrenal_gland.html

• pair of glands each having a flattened pyramidal shape
• has two distinct regions different in structure and function-- the adrenal cortex and the adrenal medulla
• the adrenal cortex which is located in the periphery is responsible for the production of steroid hormones
• the adrenal medulla which is centrally located produces the catecholamine hormones: epinephrine, norepinephrine and dopamine

• Pancreas

IC: http://www.umm.edu/graphics/images/en/17194.jpg

• has endocrine and exocrine functions
• with islets of Langerhans
• each pancreatic islet has cells that produce a different hormone:
• A cells produce glucagon
• B cells produce insulin
• D cells produce somatostatin
• F cells produce pancreatic polypeptide

• Gonads (Ovaries and Testes)

IC: http://media.web.britannica.com/eb-media/52/62652-004-1D1AE392.gif

• the ovaries produce two estrogens and progesterone that, together with the gonadotropic hormones, promote the development, regulation and maintenance of female secondary sex characteristics
• the said ovarian hormones also play a role in the regulation of the menstrual cycle and oogenesis
• the ovaries also produce relaxin and inhibin
• the testes produce testosterone, which promote the development, regulation and maintenance of male secondary sex characteristics

• Pineal Gland

IC: http://www.fluoridealert.org/CMSTemplates/FAN/images/pineal.gif

• responsible for the secretion of the hormone melatonin (body's biological clock regulation)

• Thymus

IC: http://cancerbioucd.files.wordpress.com/2011/05/thymus_spleen.jpg

• produces thymic factor (TF), thymic humoral factor (THF), thymosin and thymopoietin
• the hormones produced by the thymus play a role in immunity-- the maturation of T cells
• the hormones are also responsible for the retardation of aging

Hormonal Imbalance: Good or Bad?

As a medical technology student, I can say that I have a rich background on some lifestyle diseases. One of which is diabetes mellitus (DM). I have friends whose parents have diabetes. With the help of my research on endocrinology, I was able to understand how this most common endocrine disorder works on the body.


People who have diabetes mellitus are unable to produce nor use insulin. A person with type 1 diabetes has a low insulin level because their immune system destroys the beta cells found in the islets of Langerhans. These cells, as discussed earlier, are responsible for insulin production. People with type 2 diabetes, the more common type, have a problem, not with insulin shortage, but with the insulin receptors-- there is down regulation and loss of sensitivity to insulin.

An individual with dwarfism.

IC: http://www.ayushveda.com/magazine/wp-content/uploads/2008/07/dwarfism.jpg

Another endocrine disorder which I think most people are quite familiar with is pituitary dwarfism.  People with dwarfism have trouble with the production of the human growth hormone of the anterior pituitary gland. hGH hyposecretion slows down the growth of bones and could also hinder the growth of other organs. The next time you see an old person with childlike body proportions, he/she may have pituitary dwarfism.


Other endocrine disorders include diabetes insipidus (antidiuretic hormone problem), hyperthyroidism (thyroid gland disorder) and Cushing's syndrome (cortisol hypersecretion). There are more of these disorders and as we enter deeper and move along the realm of endocrinology, they will also be discussed.

So the next time you experience something different about yourself (especially if it is physiologic), consider your SILLY HORMONES-- the products of the chemical communication network of your body which is the ENDOCRINE SYSTEM.


Thank you for reading my very first blog entry! Do watch out for the next. God speed!

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References:

• Principles of Anatomy and Physiology Vol. 1 12th Ed. by Gerard J. Tortora and Bryan H. Derrickson (2009)
• Understanding Psychology 8th Ed. by Robert S. Feldman (2008)
• Basic Clinical Endocrinology 4th Ed. by Francis S. Greenspan and John D. Baxter
• Clinical Chemistry: Theory, Analysis and Correlation 2nd Ed. by Lawrence A. Kaplan and Amadeo J. Pesce