Ectopic thyrotropin secreting pituitary adenoma concomitant with papillary thyroid carcinoma: Case report

Ectopic thyrotropin (TSH)-secreting pituitary adenomas are exceedingly rare. To date, there are only 6 cases reported. Here, we describe an even rarer ectopic TSH-secreting pituitary adenoma (TSH-oma) concomitant with papillary thyroid carcinoma.

A 27-year-old female was admitted to the hospital in 2002 for neck enlargement and palpitation. Thyroid function test showed increased thyroid hormones and unrepressed TSH. Thyroid ultrasound examination displayed diffuse goiter. The patient was presumptively diagnosed as primary hyperthyroidism and treated with anti-thyroid drugs. Her condition was then improved, but the serum TSH was persistently unrepressed. Therefore, central hyperthyroidism due to TSH-oma or pituitary resistance to thyroid hormone (PRTH) was suspected. Pituitary magnetic resonance imaging (MRI) examination was deservedly performed to rule out TSH-oma, which turned out to be normal. In addition, T3 suppression test was negative. Thus, PRTH, as an uncommon cause of inappropriate TSH secretion, was regarded as the working diagnosis. Triiodothyroacetic acid, which was reported to be effective for PRTH, was then administrated. But it did not work well. To control the symptoms completely and normalize the level of thyroid hormones, radioiodine therapy was carried out in 2007, followed by levothyroxine replacement therapy. Consequently, the symptoms were relieved, whereas serum TSH remained at high levels even with adequate levothyroxine. Unexpected, thyroid papillary carcinoma and a neoplasm in her nasopharynx were successively detected in 2012, which were then removed by surgery. Somewhat interestingly, the serum TSH declined to normal after the operation.

The patient was ultimately diagnosed as an ectopic TSH-secreting pituitary adenoma concomitant with papillary thyroid carcinoma.

Thyroidectomy and removal of the ectopic TSH-secreting pituitary adenoma by surgery were carried out, followed by levothyroxine replacement therapy.

Three years after the surgery, the patient felt well with levothyroxine 125ug daily. Serum thyroid hormones and TSH kept in normal and no signs of neoplasm recurrence.

Although extremely rare, ectopic TSH-secreting pituitary adenoma, as an uncommon cause of thyrotoxicosis, should be taken into consideration among those who have a longstanding hyperthyroidism with unsuppressed TSH.