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The endocrine system

Hadyn Luke posted this on Friday 10th of May 2013 Hadyn Luke 10/05/2013

Tags: Anatomy and physiology


The endocrine system

This blog provides an overview of the endocrine system: what it is and how it functions. Any personal trainer or fitness professional should have an awareness of the endocrine system as it can have an effect on a client’s moods and their ability to carry out fitness training.

What is the endocrine system?

The endocrine system synthesises and secretes hormones, which help to regulate bodily functions, or homeostasis – in other words, keeping the body in balance. It can have both physiological and psychological effects, from sexual function to our daily moods.

While a healthy endocrine system is essential for optimal physical and emotional development during childhood and the teenage years, it continues to have a bearing into adulthood on such things as maintaining a healthy body weight. As personal trainers often work with clients looking to lose weight, it’s useful to be aware of the effect an imbalance in the endocrine system can have.

What areas of the body are regulated by the endocrine system?

The areas that the endocrine system controls include:

  • Growth and development
  • Response to stress and injury
  • Absorption of nutrients
  • Energy metabolism
  • Water and electrolyte balance
  • Reproduction, birth and lactation

These can affect how well a client performs when working with a personal trainer in the gym or taking part in a fitness class.

How does the endocrine system function?

The endocrine system works in conjunction with the central nervous system. However, whereas the central nervous system can send instant signals, those released by the endocrine system can take days or even weeks to reach the cells, muscles and organs they are travelling to.

As well as organs, the endocrine system includes glands, which secrete the hormones that transfer information from one organ to another, allowing the body to monitor its activities. Each of the 20 or so major hormones secreted through the endocrine system contribute towards the normal function of the body.

The function of the pancreas

Fitness professionals, especially those working with clients with diabetes, will be aware that the function of the pancreas is to release insulin to help the body absorb sugars from the blood. However, although insulin is a hormone, the pancreas is commonly considered part of the digestive system rather than the endocrine system. 

What makes up the endocrine system?

The major glands that make up the endocrine system are:

  • Hypothalamus
  • Pituitary gland
  • Adrenal glands
  • Thyroid
  • Parathyroid glands
  • Pineal body
  • Reproductive glands


Located in the brain stem, this is the main neural control centre.  When messages are received from the nervous system, the hypothalamus will produce chemicals that inform the pituitary gland to release hormones that regulate a variety of bodily functions.

Pituitary gland

Found beneath the hypothalamus, it is affected by a variety of signals, including our emotional state and even the weather. In seasons when there is less sunlight, a personal trainer may have clients affected by Seasonal Affective Disorder (SAD): when the pituitary gland is not producing sufficient melatonin. The adrenal, thyroid and reproductive glands are directed by the anterior lobe, which produces endorphins and growth hormones. The posterior lobe secretes hormones that control water levels and allow the uterus to contract when a woman is having a baby. 

Adrenal glands

Made up of the adrenal cortex and the adrenal medulla, the adrenal glands are found at the top of the kidneys. They help balance water and salt levels and also regulate heart rate and blood pressure when we are faced with stressful situations. 


This butterfly-shaped gland is found in the lower part of the neck, beneath the larynx. The hormones it produces stimulate the metabolism. Fitness instructors may sometimes work with clients who have put on weight and suffered digestive disorders because of an underactive thyroid.

Parathyroid glands

Responsible for controlling the amount of calcium in the bones and blood, the four parathyroids are small glands found in the neck, near the thyroid.

Pineal body

Located in the brain, it produces melatonin: the hormone that affects our sleeping and waking patterns, based on the light perceived by the body.

Reproductive glands

The ovaries and testes produce oestrogen and testosterone, which affect sexual development, from the regulation of the menstrual cycle and pregnancy in women to the development of facial hair and the function of the reproductive organs in men. Both men and women have both of these hormones in differing levels.

Diseases and conditions

If a personal trainer is working with a younger client who is not developing as they should, or an adult client who is struggling to manage their hunger or is gaining weight or growing at an unusual and hard to explain rate, they may be suffering from issues with their endocrine system. The fitness instructor should therefore refer them to a doctor or other medical practitioner for professional advice.

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