Causes of Overactive Thyroid

Pituitary Adenoma
A pituitary adenoma is a noncancerous tumor of the pituitary gland. In this case, overactive thyroid is due to too much TSH. At the time of diagnosis, most are pituitary macroadenomas, meaning they are 10 millimeters in size or larger.
Last reviewed by: Arthur Schoenstadt, MD
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