Thyrotropin-secreting adenoma in a patient with primary hypothyroidism.

OBJECTIVE

To describe a patient who developed a thyrotropin (TSH)-secreting adenoma in the setting of primary hypothyroidism.

METHODS

We report the clinical, laboratory, and radiologic findings of a patient with a history of primary hypothyroidism who presented with headache, a bitemporal visual field deficit, and elevated TSH despite long-term levothyroxine therapy. We discuss the diagnostic challenges of this case and review the relevant literature.

RESULTS

A 54 year old woman with a history of primary hypothyroidism presented with a 3-year history of headache and a week of worsening vision. Imaging revealed a heterogeneous sellar mass elevating the optic chiasm. Her serum TSH was 46.5 mIU/L and free thyroxine concentration was 0.1 ng/dL. The differential diagnosis included pituitary hyperplasia and a TSH-secreting adenoma in a patient with primary hypothyroidism. The pathologic characteristics of the tumor were consistent with the latter.

CONCLUSION

In a patient with an elevated TSH concentration and a previous diagnosis of hypothyroidism, it is important to consider other entities besides medication noncompliance. TSH-secreting adenomas can also cause elevated levels of TSH.