If ever your tests indicate your thyroid is underactive you can try to strengthen it before even considering a medication.
Once you start on the doctor’s medication it is for life because the thyroid slowly atrophies (shrinks) and works less and less.
With time, the dosage for the medication needs to be increased to maintain a proper level of hormones. But if you strengthen it for 1 year or so, usually the thyroid becomes stronger and you do not need to maintain a supplement all the time.
It is a good idea to support the thyroid in higher period of stress to make sure it will not crash again. If your tests indicate a normal function, keep in mind that medical test only pick up thyroids that function at less than 50% of their potential.
At 60% the test will say everything is normal but the person might have symptoms: subclinical hypothyroidism.