Thyrotropin-producing microadenoma associated with pituitary resistance to thyroid hormone

• Published in: The journal of clinical endocrinology and metabolism Vol. 76; no. 4; p. 1025
• Main Authors: Watanabe, K, Kameya, T, Yamauchi, A, Yamamoto, N, Kuwayama, A, Takei, I, Maruyama, H, Saruta, T
• Format: Journal Article
• Language: English
• Published: United States 01.04.1993
• Subjects: Adenoma - diagnosis; Adenoma - metabolism; Adenoma - pathology; Adult; Drug Resistance; Female; Humans; Immunohistochemistry; Magnetic Resonance Imaging; Microscopy, Electron; Pituitary Gland - drug effects; Pituitary Gland - surgery; Pituitary Neoplasms - diagnosis; Pituitary Neoplasms - metabolism; Pituitary Neoplasms - pathology; Postoperative Period; Thyroid Gland - diagnostic imaging; Thyroid Gland - pathology; Thyroid Hormones - pharmacology; Thyrotropin - biosynthesis; Thyrotropin - metabolism; Thyrotropin-Releasing Hormone - pharmacology; Tomography, X-Ray Computed; Triiodothyronine - pharmacology
• ISSN: 0021-972X
• DOI: 10.1210/jc.76.4.1025

A 21-yr-old female with hyperthyroidism is described. Though her serum-free T3 was 17.8 pmol/L and free T4 was 60.2 pmol/L, TSH was as high as 10.7 mU/L. TRH stimulated an increase in TSH from 10.7-91.7 mU/L. T3 administration in gradually increasing doses of 100, 200, and 400 mg/day resulted in gradual reduction in serum TSH. Cranial computed tomography and magnetic resonance imaging revealed a microadenoma of the pituitary gland. Histology of the surgical specimen showed a TSH-producing adenoma with TSH cell cluster islets and decreased numbers of TSH cells in the nonneoplastic pituitary. Cultured cells from the adenoma secreted TSH spontaneously and in response to TRH. This TRH-stimulated TSH secretion was suppressed by T3 in a dose-dependent manner. One year postoperatively, neither residual tumor nor recurrence were seen by computed tomography and magnetic resonance imaging. However TSH, as well as free T3 or T4, was still high and overresponsive to TRH.