What long term effects of thyroid replacement hormones are common?

If you take. The correct dose of brand name T4 replacement to keep your thyroid levels normal, the long-term effect is normal thyroid physiology. There are no abnormal or dangerous long-term effects with the correct dosage, it's as if your thyroid were functioning normally. Either T3 (liothyronine) replacement or the so-called armour thyroid, on the other hand, can be dangerous.