As far as I know with Hashimotos you can have more frequent swings with your thyroid. My first year of diagnosis I had blood draws every 10 weeks to try to get a decent reading of what my thyroid was doing. My doctor only made very small changes at at time though to try to avoid additional swings. By small I mean typically 10mg changes at a time.

A therapist I saw a while back suggested a thyroid disorder as I had certain ups and downs (lot of energy, semi-manic and then big crashes of fatigue, seemed like could be depression) that could look like bipolar but none of the behavior cues that go with it being a mental health issue. Sadly, I think sometimes thyroid conditions are misdiagnosed as depression or bipolar because of the swings you see in Hashi's. I was glad that that therapist was well enough informed to notice the difference (though, sadly, I didn't get the official Hashi's diagnosis for a few years later).

As for when things go up or down, they don't really know. They just know that an "attack" can happen where the body had an autoimmune response that attacks the thyroid or related hormones (go hypo), the body creates more hormones (if still able to) to compensate then when the body stops attacking, you end up hyper because of the excess hormones. Over time, your thyroid deteriorates and you can't make enough hormones to compensate and you just end up more and more hypo.

Why these "attacks" happen isn't really understood just like a lot of other autoimmune diseases. Some people notice that certain foods can be triggers and will alter their diet to see if they even out more -- gluten from grains and lactose and casein from dairy appear to be the most common. You'll see quite a few stories from people on this board or other thyroid boards that will say starting an elimination diet helped them figure out which foods they were having a reaction to and didn't realize it until they eliminated it from their diet. Then, editorgrrl will probably post her quote from the Mayo clinic that says no diets have been proven to make a difference. I think it's a misplaced quote as the medical community doesn't know what sets off a lot of autoimmune responses, so all we're really left with is anecdotal differences from others.

I personally found that I did better with gluten out of my diet (despite what the Mayo clinic says about diet not being important), but I didn't notice a difference with anything dairy related or otherwise (yet). Some say they also are very sensitive to nightshades, though I don't notice a difference personally (though, to be fair, I don't eat a lot of nightshades anyway).

One thing that has been shown to help is a daily dose of selenium -- 200 mg. -- for Hashi's patients. So many people supplement with that since it doesn't hurt you if it doesn't work.

In the end, they don't really know all that much about the whys behind Hashi's and the manifestation is often a lot different for meany. Some like editorgrrl get diagnosed rather easily and respond to treatment of synthetics rather well. Others haven't been so lucky and there is a lot of trial and error involved -- from doses of synthetics, to switching to the naturals, to eliminating things from their diets, from altering exercises routines, etc. We semi-jokingly call it figuring out how to "align our stars" as there seems to be a lot of variance among the individuals.

For what it's worth, my doc who is a thyroid and metabolic disorder specialist, says that he's found that his Hashi's patients tend to fare better on the naturals versus synthetics, though he freely admits that why this is isn't completely clear. He speculates that it's either because the naturals also have T3 in them whereas most synthetics are only T4 (unless you're also taking cytomel which is T3) or because that there is some benefit to having the other thyroid hormones in there that we don't currently understand. The naturals also have T1 and T2 as they're derived from cow or pig thyroid. We don't know what T1 and T2 do yet, but my doc speculates that that may part of the reason that he sees in his practices that his Hashi's patient do better on the naturals.