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usually causes Ovulatory disturbances and there is problem of egg growth or maturity. I am not very sure that it will also cause implantation
failure. There are high incidence of patients with autoimmune thyroiditis
to be associated with endometriosis
which itself can cause infertility
and implantation failure. There is no point in going ahead with IUI again. You need to undergo laparohysteroscopy to identify the underlying cause and to test patency of fallopian tubes. You can try 2 cycles of IUI immediately after surgery. If IUI fails then IVF ( Test tube baby ) is last resort. Continue taking thyroxin and regular follow up with thyroid profile is required.