I have hypothyroidism. i started with ethroxine 25mcg.later had to increase dose and now taking thyronorm 100mcg for years. when can i go back to 25mg?

Hypothyroidism: I tried to look up "ethroxine" in www.drugs.com which includes international drugs name but had no success. Google didn't give me an answer either. Thyronorm is a brand of Levothyroxine that is sold in India. Presumably you started at 25mcg & gradually increased dose to 100mcg. Goal of treatment is not to reduce dose but rather to offer appropriate dose to maintain TSH 0.45-4.5 w/o signs&symptoms

Usually never.: When the thyroid fails it is almost universally permanent. Doses may escalate but rarely decrease. The dose of levothyroxine ( thyronorm ) should remain stable all your life unless of course you lose a major body part or try to become pregnant. The goal is usually to keep your TSH at about 0.5 - 2.5 range.