My wife aging 31 has thyroid problem. Tsh test result is 56.9. What's the best medicine for this? We're planning for kids. Will it affect pregnancy?

Thyroid hormone. Your wife's thyroid is clearly failing. She needs to be on thyroid hormone (synthroid (thyroxine) or equivalent). This is a simple and safe medication to correct the thyroid levels. It is essential that this be corrected before pregnancy and that the levels are monitored during the pregnancy to make sure that they remain normal.