What else can cause pituitary hyperplasia? nonpregnant, 38/f, controlled hypothyroid, pit. labs normal. has grown in size, doesn't seem to be adenoma

Pituitary cells may: increase in number due to physiological (normal function) or pathological (disease) causes. Pituitary cell proliferation can be influenced by the releasing hormones governing other glands: adrenal, thyroid, gonads as well as growth hormone. The loss of inhibitory hormones for these glands can also contribute. You need a careful evaluation and work-up from a glandular/endocrine specialist.