thank you for posting your query in healthcaremagic.com..... well you are diagnosed with hypothyroidism... hypothyroidism can cause difficulties in pregnancy but getting euthyroid by taking medications before pregnancy helps a lot and decreases the risk for many folds.... the time taken to control the TSH levels depends entirely on the patient and it can be assessed by checking the levels on a regular interval... so dont be worried.... the drugs will be effective....just keep getting checked by your doctor regularly... and hopefully you will have a happy motherhood.... hope that was helpful... regards