Three women with pituitary enlargements associated with preexisting target organ failures are reported. Two pituitary enlargements owing to primary hypothyroidism and one to primary hypogonadism were shown to be regressed on computed tomography after the replacement therapy. Clinically and pathologically, the differentiation of a pituitary hyperplasia from a pituitary adenoma is often very difficult. Moreover, the treatments for these conditions are quite different. Adequate medication can diminish a pituitary enlargement because of the feedback mechanism. Existence of the target organ deficiency should always be checked before the management of pituitary tumor.