Introduction to Endocrinology

Written by Ben Bunting: BA, PGCert. (Sport & Exercise Nutrition) // British Army Physical Training Instructor // S&C Coach.


The endocrine system is the body's hormones which control biological processes in the body which contribute towards physical performance and regulate testosterone.

In this article we shall cover the following:


Have you ever wondered how the meal before your gym gets stored into your muscles and liver for later use?

How the glucose is efficiently distributed in various parts of your body like the brain so you can brainstorm?

Keeping a constant energy supply (glucose) around the clock is essential for the normal working of humans.

This feat and many other feats like this are carried out by special, chemical messengers – hormones

Simply put, endocrinology is the study of hormones and the disorders related to them. More precisely, where and how hormones are produced, how they are secreted, and how they act on numerous cells and tissues of the body to bring off various effects.

Hormones are produced by specific organs called glands and they are present in various locations across the body including the brain and abdomen.

These hormones once produced are secreted into the bloodstream directly where they travel to the required destination.  

The chief function of endocrinology is to maintain homeostasis, which is a state where substances within the body are kept at optimum levels for good health.

Our bodies have complex designs and they require multiple systems for check and balance. Hormones do this job effectively.

A combined effect of various hormones (interplay) to bring out an effect and make sure it is executed in the best (healthy) way possible.

Disturbance in a single hormone can have deleterious effects on the body and the study of endocrinology also covers these endocrine-related pathologies (diseases).  

The Endocrine System

introduction to endocrinology

The endocrine system is a regulatory system of the body. As mentioned above, hormones act as the messengers in this regulatory loop of endocrinology. This specialized system consists of various glands including:

We will discuss some of the important endocrinological organ systems and their related diseases. 

Hypothalamus and Pituitary Endocrinology

The hypothalamus is a gland situated in the brain that releases mostly regulatory hormones. It acts via the pituitary gland and influences almost every tissue in the body.

The hypothalamus releases several releasing hormones like a gonadotropin-releasing hormone (GnRH) which acts on the pituitary.

Consequently, luteinizing hormone (LH) is released which further regulates the reproductive organs like testes and ovaries. 

The pituitary gland, also known as the master gland, is the store for numerous hormones. they include growth hormone (GH), LH, follicle-stimulating hormone (FSH), thyroid-stimulating hormone (TSH), and prolactin.

It is known as the master gland as it modulates growth, metabolism, reproductive health, and so on…. Most of the other glands (e.g., thyroid gland) work under the pituitary’s control. If the thyroid gland produces excess hormone it is inhibited by the pituitary gland.

Having abnormalities in the hypothalamus or pituitary can cause serious lifetime consequences. Some of these conditions include:

  • Hypopituitarism – depressed function of the pituitary gland can cause dwarfism, hypogonadism (low testosterone levels), infertility, lethargy, obesity, etc. 
  • Acromegaly and gigantism – due to excess GH
  • Galactorrhea – abnormal milk secretion from the breast; due to increased prolactin
  • Cushing’s disease – due to excess ACTH
  • Hypo or hyperthyroidism
  • Pituitary tumors
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    Pancreas Endocrinology

    If you’re wondering which gland helps regulate glucose in the body, the answer is the pancreas. It is located under and behind your stomach.

    It secretes hormones such as insulin, glucagon, IGF-1, somatostatin, etc. Most of these hormones’ function is to maintain the food stores of the body such as glucose and glycogen.

    They also interplay and modulate the effects of other hormones like GH. Some diseases related to pancreatic endocrinology include:

    • Diabetes mellitus – type 1 and type 2. These are caused by problems with insulin, a hormone produced by the pancreas that helps to store glucose in the body. 
    • Pancreatic cancer
    • Glycogen storage diseases
    • Pancreatitis
    • Cystic fibrosis
    • von Hippel-Lindau disease

    Thyroid Hormone Endocrinology

    The thyroid gland is located on the front of your neck. This small gland is one of the most crucial glands for maintaining a healthy metabolism and is one of the most disease-causing glands.

    The thyroid hormone produced by this gland, is under the hypothalamus-pituitary control. Thyroid hormone primarily induces metabolic activity in the body i.e., using substrates like glucose to make energy and heat.

    This hormone is also vital for cognitive development, especially at an early age, the development of the physical characters, and even reproductive development. 

    Major diseases associated with the thyroid hormone include:

    • Hypothyroidism – low thyroid
    • Hyperthyroidism – excess thyroid
    • Thyroid cancers – follicular cell cancer of the thyroid
    • Goiter
    • Grave’s disease
    • Cretinism and mental retardation
    • Obesity

    Adrenal Endocrinology 

    introduction to endocrinology

    Adrenal glands are located on top of the kidneys. They secrete hormones like cortisol, aldosterone, and androgens (testosterone-like hormones) which act to maintain the body’s salt and water content, stress coping, secondary sexual characteristics.

    Adrenal glands also release epinephrine and norepinephrine, the body’s fight and flight hormones.

         Pathologies of the adrenal gland include:

    • Cushing syndrome
    • Hyperaldosteronism
    • Pheochromocytoma
    • Adrenal tumors
    • Hypertension

    Gonadal Hormones Endocrinology

    Gonads refer to the sex hormone-producing organs. In males, this function is carried out by testes and ovaries do this job in females.

    Gonads produce sex hormones that are required for sexual reproduction, libido, secondary sex characteristics (beard in males; breast in females).

    Other functions include bone growth, cognitive development, etc., and these are carried out in concert with other hormones like thyroid and pituitary. 

    Abnormalities of the gonadal endocrine system include:


    The endocrine system is a vast yet vital multi-organ system of the body. There is not a single organ in the body that does not receive some form of hormonal stimulation and acts accordingly.

    Whether you’re calmly enjoying your meal or you are being chased by a dog, the complex system of hormonal messaging is the key to survival and growth. 

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