Should Thyronorm Be Taken Through Out The Life?

hi,

i m 28 yrs old n married n also planning for baby....my due date of mensuration was 23rd ofsep but it was not happened till now......m not pragnent....went through some test of fasting insulin it was29.10 however thenormal should be below 24 also my TSH came 4.91.......doctor has recommended thyronorm 50 mg . i m afraid of taking tablet what should i do ? do i will have to take medicine throughout my life ?

regards,

pooja