Bc of clen's potential (and that of all thermogenics) to decrease thyroid function and "downregulate" metabolism, it reasons that supplementing with thyroid hormone while on clen is a good idea. Personally I just don't think clen works well for everyone. If someone is going to add thyroid hormone to their stack they need to take a certain dose bc the thyroid will self adjust in up to 6 weeks.
The normal replacement dose for a young (< 60yrs) healthy person of synthroid/T4 is 1.7mcg per kg, so dosing at 2mcg per kg is ideal IMO as part of a weight loss/cutting stack. T3 is 4x as potent as T4, so the replacement dose calculates to 0.43mcg per kg and 0.5mcg per kg for a weight loss/cutting stack. Of course this should only be temporary bc the long term effects of hyperthyroidism are significant and many.
I posted this in another thread recently but I think an ideal base stack for cutting would be moderate dose test (500mg/wk), hgh (> 4iu per day, 5 to 7 days per wk), and T3 (25mcg 2x per day, assuming you weigh 100kg, and start at 12.5 2x per day). Add to this tren and/or anavar and and the results should be significantly more dramatic. Tren no doubt greatly increases nitrogen retention even in calorie deficient states and will allow the addition of LBM while cutting, while weight loss on anavar has been shown to be permanent in most individuals.
Before everyone attacks me, the fact that cutting is achieved primarily through dieting, well that goes wo say and the focus above is on pharmacological enhancement.