Deelou - I don't have hypothyroid so can't help with that. I think that WW can work with most challenges and that anyone will lose weight if you have a calorie deficit where you burn more calories than you take in. If you burn fewer calories due to your thyroid issues then perhaps eat your minimum at WW (which would probably be 26 points plus a day) and don't eat as many weekly points. Also activity such as walking may help with burning more calories.
Update on me - I weighed in Friday for a .6 loss. Not great but I was very inactive for 2 weeks due to allergies. So I was just happy to have a loss. I weighed myself Saturday morning and was down .8 from Friday morning so was a little chagrined that loss didn't show up until the day after my weigh in! Hope that means I'll have a good weigh in next Friday. For my at home weigh in (which I do in the morning without clothes) I was at 179.3 Saturday morning which put me in the 170s for the first time since mid-2012. I'm not in the 170s yet for my official WW weigh in. Hope to get there this next Friday. My main goal for March is that I want to get below 175 as that would put me in the overweight category.