When treating hypothyroidism, we have the choice of using natural or synthetic thyroid hormones. Proper diagnosis by gathering relevant history, doing a physical exam, and using thorough laboratory testing is what determines which type of thyroid hormone to use.
Over the past 20+ years, I have seen many patients with symptoms of unresolved hypothyroidism whose other doctors were basing their thyroid prescriptions solely on one thyroid function test, the TSH (thyroid stimulating hormone).
My training taught me to treat the patient, not just the lab results. After ruling out other causes of their symptoms with extensive questioning and testing, I had to resort to trial and error to find the thyroid doses that worked safely without any side effects. By listening carefully to my patients and implementing therapeutic trials, many returned to normal health.