What is the Endocrine System

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Endocrine System 101

Healthylife Pharmacy24 August 2017|4 min read

What do diabetes, thyroid disease, and irregular menstruation have in common? They're all conditions of the endocrine system. You've heard of the nervous system, cardiovascular system, and the gastrointestinal system. Easy – the nervous system involves nerves, the cardiovascular system deals with blood and breathing, and the gastrointestinal system is all about digestion.

But what does the endocrine system do?

It does a lot. In fact, research breakthroughs are suggesting that the endocrine system may be far more important than we once thought – it may be the most important body system of all [1].

What is the Endocrine system?

The endocrine system is made of glands and organs that produce and/or secrete hormones into the blood stream. Hormones are involved in almost all body functions, including growth, sexual function, sleep, mood, and more.

The major glands and organs of the endocrine system are:

  • Hypothalamus, pineal and pituitary glands in the brain
  • Thyroid and parathyroid glands
  • Adrenal glands
  • Pancreas
  • Ovaries
  • Testicles
  • Adipose (fat) tissue
  • Kidneys
  • Gut

All of these glands and organs secrete hormones which travel through the blood stream and affect the activity of particular cells throughout the body.

While a nervous system message zips from one body part to another, the endocrine system prefers to keep things slow and steady. The effects of hormones on target cells can take effect hours to weeks after being released into the blood stream, and they also stick around a lot longer than nerve impulses – this means hormones can have a stronger, longer-lasting effects [1].

Hormones can also carry a mass message to multiple cells and even multiple body parts at once – for example, every cell in the body depends on thyroid hormones to regulate their metabolism (how fast they convert oxygen and calories into energy) [4].

Functions of the Endocrine system

The study of the endocrine system is expanding rapidly, due to the ongoing discovery of new hormones and their effects on the body.

The main functions of the endocrine system are currently understood to be:

  • Homeostasis – Keeping everything in balance, from blood pressure and levels of calcium in the blood, through to mood, sleep, and temperature.
  • Growth & repair – Hormone messengers are needed to initiate cell division and wound healing.
  • Sexual reproduction – Puberty, fertility, menstruation, sperm and semen production, and libido are all governed by the endocrine system.
  • Digestion – Hormones are needed to trigger digestive fluids, movement of the stomach and intestines, and gall bladder secretions.

Because hormones are so powerful and have a long-lasting effect, the endocrine system strives to keep them at an ideal level throughout the body and blood. It does this through feedback loops.

Endocrine feedback loops

Endocrine feedback loops are designed to prevent overdosing or under-dosing the body with hormones.

  • Trigger & Response: An organ or gland detects a trigger – this could be high or low levels of hormones, nerve signals, or other chemicals in the body. The organ or gland releases hormones in response to this trigger (e.g. when there is high glucose in the blood, the pancreas secretes insulin to bring it down).
     
  • Hormone Acts on Target Cell: The hormone “docks” with the target cell and elicits the desired response (e.g. insulin signals cells to absorb glucose out of the blood).
     
  • Feedback Loop: The organ or gland detects that the trigger is off – i.e. levels of hormones, nerve signal, or chemicals have returned to normal (homeostasis). They stop secreting hormones. Hormone levels drop, initiating the trigger, and the cycle starts again.

Some feedback loops involve multiple glands and organs, and inter-connect with other feedback loops and hormone cascades [4]. Most notably are the HPA / HPG / HPT axes.

HPA / HPG / HPT Axes

The major control centre of the endocrine system is located at the base of the brain. Here, the hypothalamus and pituitary glands initiate some of the most important hormone cascades throughout the body.

These are called the “HP-axes” [3] [4].

H = hypothalamus

P = pituitary

The last letter of the acronym refers to the target tissue:

A = adrenals (to secrete stress hormones)

G = gonads (to secrete sex hormones)

T = thyroid (to secrete metabolism hormones)

When the hypothalamus detects abnormal levels of hormones in the blood, it stimulates the pituitary to send a hormone to the target tissue.

In the HPT axis, for example, the hypothalamus may detect low levels of thyroid hormone in the body. It will then secrete a hormone that is picked up by the nearby pituitary gland. When the pituitary detects the hormone, it responds by increasing its release of thyroid stimulating hormone (TSH). As the name suggests, this hormone stimulates the thyroid gland (located in the throat) to produce and secrete more thyroid hormones. Thyroid hormones circulate throughout the body and act on every cell in the body. Once the hypothalamus detects that blood levels of thyroid hormone are back to normal, it will stop stimulating the pituitary gland and the loop will stop.

The HPA axis involves the regulation of stress hormones from the adrenal glands. When stress is high, the hypothalamus and pituitary glands stimulate the adrenals to produce hormones like adrenaline and cortisol [4].

The HPG axis controls the regulation of sex hormones, including oestrogen and testosterone. The hypothalamus stimulates the pituitary to secrete luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which send signals to the gonads to secrete sex hormones. If this axis is out of balance, then menstruation may be irregular, PMS may be heightened, or fertility could be compromised.

Naturopathic medicine believes that these axes work together, and an over-active axis will throw the other two out of balance. Because we're wired for survival, the HPA axis often takes precedence, causing disruption to thyroid and sex hormones. It's often the case that stress (HPA axis) goes hand-in-hand with weight gain or metabolism issues (HPT axis), and fertility, menstrual or menopause problems (HPG axis).  

Endocrine Disorders and Diseases

Endocrine disorders are some of the most common in the world [2]:

  • Diabetes – Insulin is a hormone that signals cells to take up glucose.
  • Menstrual issues – Irregular menstruation, polycystic ovarian syndrome and menopause symptoms.
  • Thyroid conditions – Hypothyroid (under-active), hyperthyroid (over-active), and thyroid nodules are common endocrine conditions.
  • Parathyroid problems – Enlargement of the parathyroid glands can cause dangerously high levels of calcium in the blood.
  • Pituitary tumours – A tumour of the pituitary can cause the gland to over- or under- secrete hormones and ignore signals from feedback loops.

Not all hormonal imbalances are due to a disease – stress, infections, and electrolyte imbalances all cause hormone fluctuation from the endocrine system [2].

Natural Therapies to support Endocrine function

Indole-3-Carbinol

Indole-3-carbinol (I3C) is a chemical found in brassica vegetables (like brussels sprouts, broccoli and cauliflower). I3C helps to regulate the endocrine system by boosting elimination of used-up hormones like oestrogen. It is particularly effective in diabetes where it acts as an antioxidant to protect the body against damage caused by high blood glucose [5] [6].

Rehmannia (Rehmannia glutinosa)

This adaptogenic herb has been used for hundreds of years in Traditional Chinese Medicine for its endocrine-supporting actions. Rehmannia contains glycosides that help the endocrine system to produce, secrete and react to hormones that reduce symptoms of menopause, high blood pressure, and may help to treat polycystic ovarian syndrome [7] [8].

CAUTION: Do not use during pregnancy or breastfeeding.

Zinc

Zinc is essential for the release of hormones from the pituitary gland and helps to regulate sex hormones. Supplementing with zinc has been shown to normalise testosterone levels in men and women [9]. It is also used in type 2 diabetes where it helps break down carbohydrates, and reduces cell desensitisation to insulin [10]. 

Omega-3 (EPA/DHA)

Healthy fats are needed for the production and action of every hormone. Supplementing with omega-3 fatty acids may improve fertility outcomes [11], reduce menstrual irregularities and PMS [12], stabilise thyroid hormones [13], and improve insulin action in T2DM [14].

References

  1. Morley, J. E. (2016) Overview of the Endocrine System. Merck Manual.  http://www.msdmanuals.com/professional/endocrine-and-metabolic-disorders/principles-of-endocrinology/overview-of-the-endocrine-system
  2. Merck Manual Professional (2016) Endocrine and Metabolic Disorders. http://www.msdmanuals.com/professional/endocrine-and-metabolic-disorders
  3. Mitrovic, I. (2015) Introduction to the Hypothalamo-Pituitary-Adrenal (HPA) Axis. University of San Francisco, 468 – 483.  http://biochemistry2.ucsf.edu/programs/ptf/mn%20links/HPA%20Axis%20Physio.pdf
  4. Tsigos, C., et al. (2016) Stress, Endocrine Physiology and Pathophysiology. Endotext., 1:1. https://www.ncbi.nlm.nih.gov/books/NBK278995/.

    Comhaire, F. H. & Depypere, H. T. (2015) Hormones, herbal preparations and nutriceuticals for a better life after the menopause: part II. Climacteric, 18:3, 367 – 72 https://www.ncbi.nlm.nih.gov/pubmed/25668332
  5. Poornima, J. & Mirunalini, S. (2014) Regulation of carbohydrate metabolism by indole-3-carbinol and its metabolite 3,3'-diindolylmethane in high-fat diet-induced C57BL/6J mice. Mol Cell Biochem., 385, 7 – 15. https://www.ncbi.nlm.nih.gov/pubmed/24072613
  6. Ma, N., et al. (2016) [Analysis of Medication Laws for Chinese Medicine Treating Hypertension Patients with Yin Defi- ciency Yang Hyperactivity Syndrome Based on Literatures]. Zhongguo Zhong Xi Yi Jie He Za Zhi, 36:4, 403 – 410. https://www.ncbi.nlm.nih.gov/pubmed/27323609
  7. Zang, R. U., et al. (2016) Rehmannia glutinosa: Review of botany, chemistry and pharmacology. Journal of Ethnopharmacology, 117:2, http://www.sciencedirect.com/science/article/pii/S037887410800069X
  8. Prasad, A. S., Mantzoros, C. S., Beck, F. W., Hess, J. W. & Brewer, G. J. (1996) Zinc status and serum testosterone levels of healthy adults. Nutrition, 12:5, 344 – 348. https://www.ncbi.nlm.nih.gov/pubmed/8875519
  9. Jayawardena, R., et al. (2012) Effects of zinc supplementation on diabetes mellitus: a systematic review and meta-analysis. Diabetol Metab Syndr., 4:13. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3407731/
  10.  Showell, M. G., et al. (2017) Antioxidants for female subfertility. Cochrane Database Syst Rev., 28:7. https://www.ncbi.nlm.nih.gov/pubmed/28752910
  11. Behboudi-Gandevani, S., et al. (2017) The effect of omega 3 fatty acid supplementation on premenstrual syndrome and health-related quality of life: a randomized clinical trial. J Psychosom Obstet Gynaecol., 14, 1 – 7. https://www.ncbi.nlm.nih.gov/pubmed/28707491
  12. Taraghijou, P., et al. (2015) The effect of n-3 long chain fatty acids supplementation on plasma peroxisome proliferator activated receptor gamma and thyroid hormones in obesity. J Red Med Sci., 17:10. 942 – 946. https://www.ncbi.nlm.nih.gov/pubmed/23825994
  13. Chen, C., et al. (2017) Association between omega‐3 fatty acids consumption and the risk of type 2 diabetes: A meta‐analysis of cohort studies. J Diabetes Investig., 8:4, 480 – 488. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5497038/