“It’s Just Hormones”

It’s just hormones. What do you mean when you say that? Are hormones just pesky little gender-specific gremlins that can make us tearful or a bit snappy, or are they something more? Hormones are instrumental in so many processes, not just how we feel today. They don’t just regulate your moods: they regulate your metabolism, your blood pressure, and your stress response. They affect a range of functions, such as growth, sexual characteristics, reproduction, and can be transported all around the body. They’re one of the most interesting parts of biochemistry (in my opinion anyway), as even one single hormone can have such a diverse range of effects. To give just one example, vasopresin (or ADH as you may have heard it called) regulates water reabsorption in the kidneys – so it dictates how much water is in our urine, and how much remains in our bodies to keep us hydrated. This means our blood can keep moving around our bodies and we can keep living. Hormones don’t sound so trivial now, do they? It’s also likely that ADH plays a role in releasing corticosteroids (a category of hormone which includes adrenaline, another hormone you may have heard of, which plays a large part in your “fight or flight” response) from the adrenal gland to respond to stress, especially in pregnancy and lactation. It’s even been associated with pair-bonding – the ability for two mates to form a bond for one another. So if one hormone can do all these things, what actually is a hormone?

The diagram above shows the locations of the major endocrine glands in humans.

A hormone is a substance, sometimes described as a “chemical messenger” which has a regulatory purpose in our bodies (that means keeping everything in normal running order and stopping things getting out of hand) and which stimulates activity in cells and tissues. Hormones are produced by “endocrine glands”, such as the adrenal gland at the top of your kidneys, the pituitary gland at the base of the brain, the testes, and the ovaries (come on, you know where those are). The word we use to describe the collection of glands that release hormones into our circulatory system is called the endocrine system; this is not to be confused with the exocrine system, which is a collection of glands which release products such as sweat and saliva, which do not enter our bloodstream. Problems with hormones and endocrine glands can cause a range of effects, depending on the type of hormone affected, including diabetes, hyperthyroidism and sleep disorders – not just mood swings! There are different types of hormones: Steroid Hormones

Chemical structure of estradiol, a type of estrogen. Estradiol is important in regulating the menstrual cycle in women, and also has a role in male reproductive systems.
Chemical structure of estradiol, a type of estrogen. Estradiol is important in regulating the menstrual cycle in women, and also has a role in male reproductive systems.

These might be my favourite type of hormones (yes, I’m a bit of a nerd if you didn’t know it already). Steroid hormones are fat soluble. If you’ve ever tried to mix oil and water, you’ll notice that they separate out into two distinct layers: one of fat and one of water. In a mix like this, fat soluble molecules will happily mix in with the oil, while water soluble molecules will separate out from oil, and mix with water. Being fat soluble enables steroid hormones to enter cells (something other hormones are unable to do), as our cell membranes are made up of fats, which prevent most water soluble molecules from getting in. This means these hormones are able to interact directly with our DNA, which is inside the nucleus of the cell, while other types of hormones cannot, as they are unable to get past the cell membrane. Examples of these are the sex hormones: estrogens, androgens (such as testosterone) and progesterones; all three of these types are made by both males and females and stimulate development of sex organs and secondary sexual characteristics, such as breast growth in females, hair growth (in both males and females) and deepening voices in males. Note: these are all steroid hormone types, and within these categories are similar hormones with different functions. Amino Acid Derivatives

The amino acid, tryptophan can be made into melatonin.
The amino acid, tryptophan, pictured above, can be made into melatonin, pictured to the left, by making a few changes to the structure.
Melatonin is an amino acid derived hormone. By comparing this image to the one below, we can see that it shares a similar structure to the amino acid, tryptophan.
Melatonin is an amino acid derived hormone. By comparing this image to the one to the right, we can see that it shares a similar structure to the amino acid, tryptophan.

Don’t be deterred by the complicated-sounding name of this type of hormone. These are small water-soluble hormones, made from amino acids (the building blocks of proteins) and are unable to enter our cells. They bind to receptors (signalling molecules) on the outside of cells, usually triggering a chain of reactions inside the cell, leading to the activation of other molecules inside the cell, which can have a direct impact on DNA. Examples of these are adrenaline, which regulates our fight or flight response, helping us to respond to stressful situations and melatonin, which has a role in regulating our body clocks and sleep cycle. Peptide Hormones These are proteins, long chains of amino acids, and like amino acid derivatives, are water soluble, though this type are much bigger. Like amino-acid derived hormones, these molecules must bind to the outside of cells, to trigger other reactions inside the cell to be affected. Examples of these are insulin, which increases blood glucose levels when our blood sugar drops a few hours after eating, growth hormone and oxytocin.

Related articles: Are Students Naturally Lazy?, “The Love Hormone”

As always, I love hearing your thoughts, so feel free to leave your reply, like or even send me a tweet!

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