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What was the reason that you had your thyroid checked? Do you have a history of thyroid disease? Have you had your cholesterol checked? The number you provided is consistent with subclinical hypothyroidism. That is a low function of your thyroid that would not account for your low body weight.
We usually do not do anything about these findings except to monitor them. I would recommend that you have your thyroid checked again in one to two years. I also recommend that you have your cholesterol checked and followed if necessary. If you develop any symptoms related to hypothyroidism, then you should see your physician immediately. Symptoms include heat intolerance, changes to your skin or hair, weight gain or loss.