In women, there are two regulatory reproductive hormones that get a lot of attention: oestrogen and progesterone. Now, while these are incredibly important in fertility and regular cycles - we'll leave that for another day. We're here to learn about what else they do. After all, there are receptors for these two hormones all over the body.
Oestrogen and progesterone are produced endogenously (inside/by your body) by the adrenal cortex and the ovaries from cholesterol. They are classed as steroid hormones, similar to the ones found in contraceptives - however those are exogenous (from outside the body) and not exactly the same.
Oestrogen has responsibilities in other parts of your body besides your uterus, such as, your cardiovascular system, your bones, immune system, epithelial cells (skin), and your central nervous system. As an example, oestrogen communicates with the islet beta-cells in your pancreas to regulate insulin secretion. This is one reason why metabolic syndrome and diabetes come hand in hand with reproductive hormone disruption. Oestrogen is also important in energy regulation; oestrogen alpha-receptors in the brain talk to this funny thing called POMC to discuss food intake and also with SF1 (in your hypothalamus) to talk about how much energy you should use and where you should store fat. Without these receptors working properly or enough oestrogen, you would kinda want to eat all of the time. Of course, oestrogen isn't the only controlling factor here - but hormones are the master messengers. So what else does oestrogen do?
Oestrogen keeps your skin young! (along with hydration and good doses of healthy fats). Your skin changes during your cycle, the thinnest point being when your menstruating - when oestrogen and progesterone are low. The thickness builds as oestrogen increases, just like the utrerine lining! This is also why skin care after 30 is so important, as oestrogen levels naturally fall (v slowly) and collagen synthesis is less stimulated. Skin firmness, elasticity, thickness and hydration all changes with oestrogen. Keratinocytes, which make up the majority of our outermost epidermis skin layer, are more active and more proliferative with healthy levels of oestrogen. They are also protected from excess inflammation by oestrogen (to an extent), as this magical hormone inhibits production of a signalling protein (chemokines) which triggers an inflammatory cascade. All the more reason to give your natural hormones free reign.
What about progesterone then?
Well, Progesterone is largely made after ovulation by your corpus lutem - this is the scar tissue where your ovulated egg just came from. If you don't ovulate, i.e. are on the pill, then good luck making this good stuff without it being in your pill. As part of reproduction, progesterone's main role is to maintain a pregnancy - low progesterone contributes to miscarriage risk greatly. During this time, progesterone also inhibits high levels of prolactin (to prevent lactation), stimulates hair growth, and prevents contractions through the relaxing GABA receptors. This gives a clue to other actions of progesterone, whereby it has an anxiety-relieving effect. This could be through three mechanisms.
Progesterone gets metabolised (broken down) and it's metabolites positively modulate GABA-alpha receptors = relax mode.
Regulation of gene expression for inflammatory mediators and neuroprotectivity.
Activation of certain signaling cascades to change mitochondrial functioning.
If your progesterone is low, you may experience more anxiety in the second half of your cycle, as this GABA-alpha receptor interaction is just one of the ways progesterone affects our mood.
Progesterone (metabolites) also helps build strong myelin sheaths over your nerves, this helps protect nerves and enables them to pass signals on faster. Another thing progesterone helps to build, is bone. Oestrogen and progesterone both contribute to the formation of bone tissue through directly decreasing bone resorption and promoting osteoblast activity, respectively.
That's a lot of information, and by no means the end of it. I just wanted you to see the cool parts.
Did you learn anything new? Let me know in the comments what shocked you most!
*Research papers have been hyperlinked, that's why some words are green.