We report two cases with primary autoimmune hypothyroidism and an ectopic thyroid gland causing pituitary enlargement mimicking pituitary macroadenoma. One of the cases presented with complaints of headache and short stature and the other case with a complaint of menorrhagia. In both cases, the pituitary mass and symptoms resolved with levothyroxine replacement. Normal menses resumed. However, pituitary dynamic tests revealed persistent growth hormone and gonadotropin deficiency in one case and growth hormone deficiency in the other. To our knowledge, this is the first report in an adolescent of hypogonadotropic hypogonadism, growth hormone deficiency, and menorrhagia associated with pituitary hyperplasia secondary to primary hypothyroidism. The recognition of the association between reversible pituitary hyperplasia and primary hypothyroidism might eliminate unnecessary surgery.