At My Pet Nutritionist, we understand the importance of hormones in the body, and how the slightest imbalance can lead to both minor, and major health issues. This guide will help you understand the role of hormones within the body.
What are hormones?
Hormones are found in all living organisms, from mammals to plants. They are substances found in the body which regulate bodily functions, including mental development, physical development, reproduction, and metabolism.
What is the Endocrine System?
The Endocrine system is comprised of all the organs and glands that produce and secrete hormones directly into the bloodstream and into the tissues and organs which use them.
Thyroid Hormones
Thyroid stimulating hormone
While Thyroid Stimulating Hormone (TSH) is produced in the brain, by the Anterior Pituitary Gland, it is the most important hormone for thyroid function. TSH is the hormone which is needed to stimulate the production of other important hormones in the thyroid gland.
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Dogs suffering from Hypothyroidism have been proven to have fluctuating amounts of TSH produced, which causes issues when trying to produce the relevant hormones in the thyroid itself, leading to Hypothyroidism.
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Thyroxine
Thyroxine, also known as T4, is the most important hormone produced in, and secreted by the thyroid gland. Tyroxine is essential for normal functioning of the heart and muscles, neurological development, digestion, metabolism and weight management, and bone repair/strengthening.
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Thyroxine supplements may help physical and cognitive abilities if used as a treatment for patients suffering with hypothyroidism.
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Triiodothyronine
Also known as T3, Triiodothyronine is another important hormone produced and secreted by the thyroid gland. It aids the control of metabolic rate, heart rate, neurological development, bone development, and digestion. It goes hand in hand with Thyroxine. Triiodothyronine is particularly important for skeletal development and function.
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Calcitonin
Calcitonin is the third important hormone produced by the thyroid, and is used in the regulation of calcium and phosphate levels in the blood. It also helps to protect the body against developing hypercalcaemia, by reducing the levels of calcium in the blood.
Where the other thyroid hormones are stimulated by TSH, Calcitonin production is also stimulated by Gastrin; one of the gastric hormones, which aids muscle growth, and contributes to muscle health in aging individuals, as well as gut motility, and production of stomach acid.
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Reproductive Hormones
Oxytocin
Oxytocin is produced in the brain, in the hypothalamus, and is released by the pituitary gland for use in the reproductive system. This is the hormone responsible for sexual arousal, and bonding between mother and infant. The uterus contracts when stimulated by Oxytocin, so it is an important hormone during labour too. Trust and recognition are also controlled by oxytocin, as well as the bond between the owner and pet.
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Progesterone
Progesterone is responsible for the preparation of the uterus lining; the endometrium. Once fertilized, the eggs will embed themselves in the endometrium, where they will grow and mature.
Relaxin
Relaxin is utilised in both the musculoskeletal system, and the reproductive system. In the reproductive system, it aids the growth of the placenta, and also helps imbed the fertilized egg (embryo) into the endometrium. In the musculoskeletal system, Relaxin is involved in cartilage and tendon health, as well as bone and muscle repair
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Testosterone
Testosterone is particularly important for males, however it is present in females too. In females it regulates breast tissue, and fertility. In males, testosterone not only aids sex drive, but also regulates distribution of body fat, bone density and muscle mass, and it also aids the production of Red Blood Cells, and sperm.
When testosterone is taken away too early, through premature neutering, the risk of a huge variety of health problems can increase, including weight gain, arthritis, uneven bone growth, poor bone strength, various cancers, among other health issues.
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Adrenal Gland Hormones
Cortisol
Cortisol has many functions in the body. It is produced in the Zona Fasciculata, which is in the very centre of the Adrenal Gland. It’s functions in the body include controlling the body’s intake and use of protein, fat and carbohydrates, increasing blood sugar levels, decreasing inflammation, and regulating blood pressure.
Cortisol is also known as the ‘primary stress hormone’ – it’s the hormone which helps relax urges of stress or anger, and helps build the bond between owner and dog, alongside the aforementioned Oxytocin.
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Adrenaline
This one may be quite self-explanatory. When you think of what it feels like to have an adrenaline rush; this is the role of adrenaline! It causes an increase in blood pressure, expansion of passageways to and from the lungs, heightened pain threshold, more acute sensitivity to sounds and sights, and is also very important for distributing blood to muscles.
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Aldosterone
Produced in the adrenal glands, Aldosterone is responsible for regulation of water to salt ratios in the body. The amount of salt to water in the body dictates blood pressure, so Aldosterone is essential in the regulation of normal, healthy blood pressure.
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Noradrenaline
Produced in the adrenal medulla, this is an important hormone used by the brain. It regulates cognitive function at all ages, and is also an important part of arousal and attention span.
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Pancreatic Hormones
Insulin
This may be a hormone you most likely will have heard of. Insulin is a massive part of diabtetes. Why is this? The role of insulin is to lower blood glucose levels. Type 2 Diabetes is caused by a spike in blood glucose levels, where insulin is not present enough. This hormone is produced in the pancreas.
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Glucagon
Alongside Insulin, Glucagon is also produced in the pancreas, and also helps regulate glucose levels within the body. Glucagon regulates glucose homeostasis by stimulating the production of glucose form the liver.
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Somatostatin
Produced in the pancreas, Somatostatin inhibits the secretion of insulin and glucagon, which is useful in the stopping of endocrine-secreting tumours, such as glucagonomas, insulinomas, carcinoid tumours, and some gastric tumours. It also helps to regulate the production of stomach acid.
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Ghrelin
Ghrelin is one of the many hormones in the body, which stimulates production of another hormone. In this instance, it is produced in the pancreas, to stimulate the production of glucagon. It is thought that Ghrelin also plays a role in the reduction of glucose storage in major organs.
Ghrelin is also involved in appetite stimulation in dogs.
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Secretin
The final pancreatic hormone we will discuss, is Secretin. This hormone is heavily responsible for the regulation of pancreatic bicarbonate (which regulates pH – too little pancreatic bicarbonate and the pH may be too acidic, too much, and the pH may be too alkaline). Secretin is also important for regulation of stomach acid, and osmoregulation (the control of salt and water balance in the body’s tissues).
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Renal Hormones
Calcitriol
This hormone is essential for regulation of calcium in the plasma, working alongside the Parathyroid Hormone. Calcitriol aid absorption of calcium and phosphate from the gut, and encourages calcium reabsorption into the kidneys, as well as supporting the release of calcium stores from bones.
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Renin
Specialised cells in the kidneys produce and secrete Renin. Renin is partly responsible for the control of blood pressure. If the blood pressure drops below a healthy level, renin is released to bring the blood pressure back up to where it should be. It also maintains correct sodium and potassium levels in the body.
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Brain Hormones
Dopamine
Dopamine is a type of neurotransmitter, which means it has a huge neurological role in the body. This is the hormone responsible for the feeling of satisfaction and pleasure. Dogs may have a surge of dopamine released into their system during bonding and playtime with their owner. In an interesting study, impulsive behaviours are linked to a lack of dopamine – this can be caused by the lack of ability to tolerate a delay in reinforcement following carrying out a behaviour. Anxious behaviour can also be linked to the lack of sufficient dopamine in the brain.
Dopamine also has a renal effect; even at low doses, it increases renal flow through renal vasodilation (widening of the blood vessels to and from the area), which helps dilute urine to healthy levels before expulsion.
In the cardiovascular system, high doses of dopamine cause increase heart rate and blood pressure.
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Endorphins
This important group of hormones help relieve the body of negative stimuli, such as pain, stress, and low mood. When the body experiences any of these stimuli, endorphins are released to reduce the symptoms, and help the body cope better.
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Melatonin
Metatonin is known as the ‘sleep hormone’. This is the hormone responsible for the circadian rhythm (the body’s 24-hour cycle), and sleep. Melatonin is produced when in darkness; being exposed to light blocks melatonin production, which is why darkness during sleep times is a great idea.
Melatonin production is also useful for the immune system, and reducing the chance of depression, and as an anti-ageing support.
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Brain Natriuretic Peptides
Brain Natriuretic Peptides (BNP) are strongly related to heart health and function. Think of them as the hormonal link between the brain and the heart.
When the body undergoes pressure or stress, the heart is affected negatively, and an adaptive response is started, called Cardiac Hypertrophy. While this can help reduce the negative effects on the heart, it can also increase chance of heart failure if it occurs too often. BNPs inhibit Cardiac Hypertrophy, to reduce the risk of sudden heart failure. BNPs have been found to be higher in abundance when a dog is undergoing Myocardial Ischemia (build up of plaque in the blood vessel walls of the heart, causing partial or complete blockages of said vessels) – at the moment, there are not enough scientific studies on this subject to fully understand why there is an increased presence of BNPs during this time.
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We hope this article has been informative with regards to many of the important hormones produced by the body, and their uses. If you require help for specific health issues, or general dietary advice, please don’t hesitate to book in with one of our team!
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