Probably postpartum thyroiditis （可能是產後甲狀腺炎）。

Normal T4 and T3 with low TSH may suggest a subclinical hyperthyroidism. The above hormone levels needs to be monitored closely. As for now, you may not need any specific treatment.  You need to follow up with your primary care doctor and your endocrinologist regularly because you are at a higher risk for the later development of  hypothyrpoidism and/or goiter.