Hormones are vital to many of our body's processes – and not just the ones in our reproductive system. From sleep to weight to stress, they play a big part in our general wellbeing.
We often talk about the need to balance our hormones, but how well do we even understand how they work? We give you the rundown on the major hormones in your body and where they're found.
There are around 50 different hormones in the human body, most of which are produced in the endocrine system.
These chemicals are then released into the bloodstream, and go on to activate certain cells. While they help to control a number of tissues and organs, hormones also play a major role in most body functions, including sleep, regulating your temperature, and growth.
Levels will fluctuate throughout the day, depending on your activity and the time, but they're also influenced by factors such as stress, age, weight loss or gain and excessive exercise.
Unlike, for example, the digestive system, the parts that make up the endocrine system are found all around the body, but because they have similar functions and are interdependent, they're considered as one system.
Here we describe some of the key glands and organs that make up the endocrine system and how they function.
This gland, found at the base of the brain, is the primary control centre of the system.
While it's only the size of a pea, it's known as the 'master gland' because the hormones it produces control several processes in the body, including blood pressure and the release of oxytocin.
The pituitary gland is also primarily responsible for regulating the thyroid, adrenal and reproductive glands.
This gland sits at the front of the throat just below the Adam's apple. It produces hormones that regulate metabolism, heart rate, digestion, temperature, brain development and bone maintenance. The thyroid relies on having a good supply of iodine to function, and it can become overactive (hyperthyroidism) or under-active (hypothyroidism).
Hyperthyroidism speeds the body's processes up, and can lead to anxiety, weight loss with increased appetite, and more frequent and heavy periods. It most commonly develops in women aged 20 to 40. On the other hand, hypothyroidism usually develops after age 40, and slows the body's processes. Symptoms of this include intolerance to cold, fatigue, weight gain and poor concentration.
Found just behind the stomach, this organ aids digestion and produces hormones that maintain healthy blood sugar levels. The most important of these hormones is insulin, which helps to lower glucose in the bloodstream and stores glucose to use for energy later.
This energy is used during exercise and fuels the parts of the brain that run on glucose. While the pancreas is usually good at keeping blood sugar stable, issues can arise when the pancreas can't make any insulin, when it doesn't make enough insulin, or when the body becomes insulin resistant.
This resistance happens when muscle, fat and liver cells can't easily absorb glucose from the bloodstream, so the pancreas needs to produce higher levels of insulin to help the cells absorb this glucose. Eventually, the pancreas can't produce enough insulin to overcome the resistance, and excess glucose builds up in the bloodstream. Over time, this can cause type 2 diabetes, polycystic ovary syndrome, cardiovascular disease and obesity.
The two adrenal glands sit above each kidney, and as the name suggests, are responsible for releasing adrenaline. They also regulate the levels of salt and water in the body. In times of acute stress, the adrenal glands produce a large amount of adrenaline in a short time, to prepare the body for the 'flight or fight' response.
They also produce cortisol, which works with adrenaline to help the body manage stress. While it's rare for the adrenal glands to become under or overactive, chronic stress can lead to an overproduction of cortisol.
Throughout our lives, the reproductive system and its hormones have a huge effect on our bodies. In women the main hormones are oestrogen, progesterone and testosterone, which are produced in the ovaries. Together they're responsible for puberty, egg production, pregnancy, birth and menopause. Oestrogen is the dominant hormone in the first half of the menstrual cycle before ovulation.
It's also an umbrella term that covers the three naturally produced oestrogen hormones: oestradiol, oestriol and oestrone. Oestradiol is the most potent of the three and is chiefly responsible for maturing and maintaining the reproductive system. Oestriol and oestrone are weaker, but no less important. Oestriol is produced by the placenta in pregnancy and can be used to measure the health of the foetus.
It's also used to predict the date of birth, as levels surge around three weeks before labour. Oestrone is produced in the ovaries, the adipose (fat) tissues and in the adrenal glands. It's the main oestrogen present post-menopause.
The other important female hormone, progesterone, regulates your menstrual cycle and is the main hormone in the second half of the cycle. It helps to thicken the lining of the uterus with nutrients in preparation for pregnancy, and if no pregnancy occurs these levels drop, triggering your period. Levels of progesterone rise during pregnancy, as the placenta produces high levels of this hormone.
In women, testosterone is used for muscle and bone strength and for the growth of normal body hair. Women with low levels of this hormone may experience lowered libido, lack of energy and unexplained fatigue. Too much testosterone can lead to irregular or absent periods, excessive hair growth, alopecia and darkened skin patches. It's also associated with polycystic ovary syndrome.
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