I really don't know much about thyroid issues and exercise so I think i'll have to look up about that! Are thyroid issues quite common Bec? Is it mainly your energy levels it effects or is it weight loss too?
Um... i think 1-2% of pre-menopausal women and 10-15% of elderly women suffer with thyroid insufficiency. The thyroid gland is in the throat an it makes thyroxine, which is the chemical catalyst of living cells. Basically it tells your metabolism how fast to work - if you build a lot more muscle you usually have more fT4 (free thyroxine4 - you also have thyroxine3 which is what your body turns the T4 into to use it, but they tend not to measure it because a situation where you have plenty of T4 but cannot convert it to T3 is incredibly incredibly rare and you'd most likely die in the womb of it) because your brain registers muscle mass as needing more "care" than fat - that's how muscle mass raises the BMR.

If you don't have enough, in not-very-scientific terms, you work slower. Your hair and eyebrows break and fall out and don't re-grow at the normal speed, your nails are brittle, your skin becomes thick and feels dry and cool the whole time, you feel cold even in the middle of summer, you have no appetite but you gain weight regardless because the body simply doesn't metabolise fast enough to keep blood carbs high and ends up converting "left over" energy the whole time because it's always "left over" having never become available in the immediate sense, your muscles don't repair at a normal speed so you might have DOMS for days or weeks, you get joint pains and strains from relatively normal actvities (i took a million supplements when i was training for the half marathon, to try and support my poor slow-grow repair systems), you start to need sleep more and more, some people i know were having 14 hours in 24 and STILL knackered, you feel tired in your limbs so that just the idea of getting up to take a cup to the sink can be daunting, your pulse rate drops (at my illest mine was 38bpm, and i know people who were ill with other things, like anorexia, who were rushed to hospital at that stage!), you stop ovulating, your periods become heavy and then infrequent, if you're BFing you can suffer low supply (not everyone does), untreated in pregnancy it can cause mental and physical development problems in bubs up to and including miscarriage, it can cause pre-term labour, placental abruption and PPH.

DOing weights twice a week and running 3-4 times you should definatly be seeing a loss What are you eating? I would think it would be something in the food or drink maybe . Have you gone up in weights yet? Remember when you can complete all the sets it's time to up it by about 10%. You could probably start to add in some extra core work to your routine now. Take away the stability from some of the exercises and you'll be adding in core work without even reaslising (actually thats a lie you WILL feel it lol!). I can't remember off hand what exercises you're doing but you have a fitball right? Instead of lunges with both feet on the floor, put your back leg on the fitball with your knee at 90* and do it like that. To stabilise yourself you have to switch on your core. If you're doing shoulder presses or chest presses (I think you are) then lay on the fitball to do them. Plank - put your feet on the fitball! Do you have a bosu? If not they are great!
I'm eating the same as i always do, about 2100/day, minus 300 (average over week according to very vague calculations of mapmyrun). I could certainly be stricter with food, but equally i am not at ALL overeating consistently, iykwim. I think the main reason the thyroid problem makes weightloss hard is that you can get into a situation where because the energy doesn't come easy i might very well go for a run in the morning, but i might then barely move from the sofa the rest of the day, so even though i exercised, overall i didn't burn more than if i'd been less active - does that make sense? Unfortunately the standard support-group type advice is "take it easy, be gentle with yourself, conserve energy for living" and i am NOT willing to drop exercise in the dedicated for-it's-own-sake sense. And in fact i know the last month i HAVEN'T been skimping on the normal activities because i walked 60km last month NOT including my runs or short journeys (i only map 4km+ walks)! I certainly feel iller than my bloods indicate i am, but it can take up to a month for the blood to reveal the situation so it could be that the flu before Christmas brought on another thyroid attack and that i'm rcovering but only now feeling the after effects.

I am finding it quite frustrating though. I can't train like normal people because even the standard "Increase runs 10%/week" rule means i get injured. If i take a week off i have to re-start 2 weeks back in training and i get sinus infections about every 7 weeks so i take one week in 7 or so off (got one now as i type - i'd run anyway but my glands are up so it's not wirth it, i'll just prolong the illness) which means it seriously takes me about 5 months to do 3 months training....

Sorry girls, this has turned into a bit of a debrief. The first year after i was diagnosed i used to think "what's all the fuss about? I'll just take the drugs and it'll be fine and i'll be like anyone else" but sadly the longer i go on with it, the more i realise that isn't true. I just need a kick up the azz because no matter how much i want a body that works like a normal one, THIS is the body i have, and if i want it to do what, and look like, i want it to, accepting it's limitations needs to be the first step in finding a way round them...

Back to the topic in hand - I've gone up in weights, yes. Also way ahead on the core - i have and use the fitball (in all the ways you listed! ) and my abs are always AGONY the next day
I'm actually really enjoying it - remember i used not to be able to do double straight-leg lifts? Now i do 3 sets of 15 holding the ball between my feet - it is SO SO HARD! But i am loving it

Bx