My friend its hard to say without some blood work to see where his thyroid levels and TIBC, ferritin and Iron saturation levels are.
There are dangers associated with High consumption of iron if the body can't rid itself of the extra build up, Hemochromatosis can be fatal if gone undiagnosed, this would be a concern if extra iron isn't needed. Is this by choice or doctor recommended?
25mcg of T3, one would think should be sufficient to supplement extreme dieting to replace low levels of Iodine. Maybe? May need more?
I'm not sure about clen,although I would only think it works under the same mechanism as caffeine, we do know caffeine interferes T3,T4 circulation and adrenal function. (The two are closely linked ) is he taking any caffeine? And supplementing with L-Turine?
Sodium and Iodine are two different minerals, both work on different pathways.
Certain foods deplete Iodine in the gut, not allowing for absorption.
And as Moen has stated genetics plays a major role.
I would highly recommend some blood work, soon pre or post competition.
Dieting can be very taxing on the endrocine system, leading to long term problems.
For your brothers sake and the future of him competing healthy, do some blood work.
Best of luck to You both, you looking out for your bro, kudos