In recent times, I have met several patients who developed hypothyroidism after giving birth. They all have a common reason: TSH was low at the beginning when they had difficulty, but after some time, TSH was higher than normal again. The reason for this is due to postpartum thyroiditis. In the early stages of thyroiditis, the thyroid follicles are destroyed by inflammation, and the thyroxine stored in the follicles is released into the bloodstream, which is the brain commanding the pituitary gland to secrete less thyroxine, and the pituitary gland receives the command to reduce TSH secretion; after a period of time, the excess thyroxine in the bloodstream is metabolized, and the thyroid follicles are not fully restored, so the synthesized thyroxine is very little, which can be seen in laboratory tests. T3T4 is low. Thyroiditis is a self-healing disease, so it can be treated without other medications. However, hypothyroidism can cause a lot of discomfort to the mother, so I personally think it is better to take a certain dose of thyroxine. Some people may say: breastfeeding with medication is not good, the medication will enter the baby’s body with the milk. In fact, there is no need to be afraid, because you are not taking other drugs, but the thyroid gland secretion of thyroxine. Let’s use an analogy: if a normal woman breastfeeds after giving birth, her milk still contains thyroxine secreted by her thyroid gland, so the baby has no problem eating it; a hypothyroid woman’s milk has less thyroxine, so she takes exogenous thyroxine to make up for her body’s needs. Then, the child will also be fine after eating her milk. Therefore, as long as the right amount of thyroxine is taken, there will be no adverse effects on the child.