A 52-year-old man presented with elevated thyroid hormone levels and an inappropriately normal serum thyrotropin (TSH) (4.0 μU/mL: normal 0.5 to 6.0 μU/mL). Computed tomography suggested an intrasellar mass without radiographic sellar enlargement. Serum alpha-subunit was elevated with flat responses of both alpha-subunit and TSH to thyrotropin-releasing hormone. Transsphenoidal adenomectomy resulted in clinical and biochemical cure with subsequent development of hypothyroidism with otherwise preserved anterior pituitary function. Pathologic studies demonstrated an 8 mm typical thyrotroph cell adenoma. Early diagnosis of such tumors requires a high index of clinical suspicion and may be facilitated in the future by utilization of highly sensitive TSH assays.
Jackson, Jeffrey A.; Smigiel, Mitchell; and Green, John F. Jr.
"Hyperthyroidism Due to a Thyrotropin-Secreting Pituitary Microadenoma,"
Henry Ford Hospital Medical Journal
: Vol. 35
Available at: https://scholarlycommons.henryford.com/hfhmedjournal/vol35/iss4/8