[A case of pseudo-TSH.PRL-producing pituitary adenoma with secondary hypothyroidism]

A 24-year-old housewife presented with weight gain of about 30 kg, constipation and pitting edema of extremity nine years after having a thyroidectomy. Hormonal examination revealed low levels of serum T3 and T4 and high levels of serum TSH and PRL. She also had enlarged pituitary gland (pituitary hyperplasia) with suprasellar extension on CT and MRI image. Thyroid replacement therapy and follow-up by MRI were performed without resort to surgery, because she had no visual disturbance. Within about 1 month after thyroid replacement therapy, serum TSH and PRL were normalized. And also thyroid function was normalized by thyronine (T3). Following this results, pituitary hyperplasia regression was seen on MRI image. About 1 year after thyroid replacement therapy, pituitary hyperplasia regression was more seen on MRI image. Prolonged hypothyroidism can result in hypertrophy of the pituitary thyrotropin-secreting cells and prolactin secreting cells. So, it can increase pituitary weight (pituitary hyperplasia). Radiological examination, abnormal sellar x-ray films suggesting intrasellar tumor are common in patients with primary hypothyroidism. Suprasellar extension of pituitary mass (pituitary hyperplasia) due to hypothyroidism was reported by radiological examination (PEG, CT and MRI image), and regression of pituitary hyperplasia was revealed by radiological examination after thyroid replacement therapy. The first choice of this type of pituitary hyperplasia is thyroid replacement therapy unless the patient has a visual disturbance. However, if this replacement therapy is not effective for diminution of the tumor, surgical removal of the tumor should be considered.