We need to think biochemically. Thyroid hormone acts by activating receptors --> activating DNA --> causing mitochondria to increase energy output. This is essentially what thyroid hormone does. It increases metabolic rate b/c it increases cellular engine speed - the mitochondria. The brain has the most mitochondria, thus the most thyroid receptors. This is why brain fog occurs - low mito fxn, low brain power. The stomach acid link is here too. The parietal cells in the stomach have possibly more mitochondria than any other cell in the body b/c they need power to pump acid uphill against a 3,000,000:1 gradient. Low thyroid will impair parietal cell fxn, which will weaken stomach acid AND intrinsic factor for B12 absorption. Now low B12 will lead to methylation issues b/c it is METHYLcobalamin - an important methyl donor. Low stomach acid and low brain are caused by many of the same problems. Mitos all over your body will not be working well either, so you feel fatigued.
Everything also is susceptible to stress so when our cortisol and adrenalin are high, sympathetics dominate. This further slows stomach output, and it also changes bloodflow from the cortical areas in brain into the more reptilian, primitive areas. Compulsiveness, anxiety, lack of attention, personality changes - the things that make us human don't function well when we are under chronic stress.
Estrogen affects everything too. It raises binding globulin in the bloodstream so even though the thyroid hormone is in the blood, it cannot activate its receptor. This is why heavy menstruation is associated with low thyroid. When estrogen is high, thyroid is low. Also, liver slows down clearance of hormones so estrogen levels rise higher still. Add to that methylation problems where detox pathways are already slowed, and the hits keep on coming.
Mitos are very sensitive to oxidative stress, to inflammation. Toxins create inflammation and that disrupts mitochondria. This is MOSTLY the reason for all fatigues, including thyroid. It is a toxin-stress equation that burns/rusts/damages our mitochondria and so all cellular function slows down. The thyroid just tries to ramp things up by going into overdrive. This wears out the thyroid, and the adrenals are also involved from the beginning too. People seem to have low thyroid, and live off their adrenal reserve, until it depletes. Then they crash.
So if you are toxic (we all are), if you are also a poor methylator (most are), and if you are stressed out (who isn't), then the entire endocrine system will be distorted. The body will make do with what it has, but some pathways will suffer more than others. The thyroid is just reacting to the imbalance. There is nothing wrong with the thyroid 90% of the time. But how many people just get drugs and are told "live with it"? How many people actually overcome their hypothyroid condition? Too few thats for sure.
We need to detox estrogens, both biological and xenobiotic. We need to get the gallbladder functioning, b/c low bile means low absorption of essential fats and A,D,E, and K. When cells are made of saturated, trans, or hydrogenated fats, they don't communicate very well. They are plastic cells b/c of plastic fats. We absolutely need omega 3's and they improve health by at least 13 different mechanisms. So GB function is needed to absorb fish oils, which are needed in the membranes of your cells. We also need choline and other important methyl donors b/c our diets are deficient, our bodies don't make enough, and we are toxic so we are using more at a faster rate. Choline helps the Liver metabolize fat too.
If you are trying to get pregnant, the risks with age can all be understood as methylation problems. See, women need lots of methyl donors b/f, during pregnancy. Without enough folic acid for example there are neural tube defects. They are 100% preventable with enough nutrition. Same with fetal alcohol syndrome. Alcohol depletes folic acid in the liver and creates a methyl deficiency which screws up development. Methyl donors are critical for all cell division so when we are little and growing, they are very necessary. To make sure you are going to have a healthy pregnancy, of course you want lots of methyl support. With age, our methylation ability drops too so this will help with that. The reason Downs Syndrome appears more often with age is the same thing. Methyl donors are depleted over time and when women become pregnant, its too late. It can be prevented with high dose, quality nutrients.
Well, lots to think about. Just know that the key to changing the body, is to change the body. Chiropractic changes position, nutrition changes composition, and they all work together.