I have hashimoto's and take synthroid for that, but over the past 3 months I've developed a painful goiter. All blood tests, ultrasounds, etc show that I have a normal thyroid function, but I also take Yaz, and started it about 4 months ago. I've heard that b.c. pills can effect thyroid function...does anyone know if oral contraceptives can cause a goiter or if in particular Yaz or Yasmin can do that?