Papillary thyroid carcinoma metastatic to the pituitary gland.

Many malignancies may present with metastases to the pituitary gland. The association of thyroid carcinoma with pituitary metastases is, however, very rare. This report describes two patients in whom metastases from a papillary thyroid carcinoma to the pituitary gland resulted in panhypopituitarism with blunted endogenous thyrotropin (TSH) production following withdrawal of levothyroxine. Both required the use of recombinant human TSH prior to radioiodine therapy. Symptoms of hypopituitarism may be difficult to distinguish clinically from those of hypothyroidism in the setting of levothyroxine withdrawal. Clinicians should be aware of the clinical and biochemical manifestations of this rare association.