Clinical and molecular studies of a thyrotropin-secreting pituitary adenoma.

Abstract

A 40-year-old woman, who had previously received radioactive iodine for hyperthyroidism, presumably due to Graves' disease, subsequently was found to have inappropriately elevated serum TSH and alpha-subunit levels and a pituitary adenoma. Detailed clinical studies revealed marked serum TSH elevations (approximately 100 mU/L) with no circadian variation, but with 7 pulses/24 h. Serum alpha-subunit levels averaged 2.5 micrograms/L, with 13 pulses/24 h. Neither serum TSH nor alpha-subunit responded to TRH stimulation, nor did serum TSH change during dopamine infusion, but alpha-subunit levels did decline slightly. In contrast, during somatostatin infusion, serum TSH declined to 30% of baseline levels, while alpha-subunit levels did not change. Pituitary adenoma tissue obtained at the time of transsphenoidal surgery immunostained weakly with anti-TSH beta serum and strongly with anti-alpha-subunit serum. Northern blot analysis of RNA isolated from the tumor revealed TSH beta and alpha-subunit mRNA levels of normal length, while primer extension analysis showed a major initiation site for the TSH beta gene that appeared to be identical in the tumor and normal pituitary tissue. A second minor upstream start site was detected in the tumor, but it represented less than 1% of transcription compared to the major downstream start site. We conclude that the tumor secreted TSH and alpha-subunit in an abnormal and discordant fashion, but that the TSH gene initiation site appeared to be normal and, therefore, did not explain the observed secretory abnormalities.

• Authors: M H Samuels, W M Wood, D F Gordon, B K Kleinschmidt-DeMasters, K Lillehei, E C Ridgway
• Journal: The Journal of clinical endocrinology and metabolism (J Clin Endocrinol Metab) Vol. 68 Issue 6 Pg. 1211-5 (Jun 1989) ISSN: 0021-972X [Print] United States
• PMID: 2723029 (Publication Type: Case Reports, Journal Article, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• RNA, Messenger
• Thyrotropin

Topics

• Adenoma (blood, metabolism)
• Adult
• Autoradiography
• Female
• Gene Expression Regulation
• Histocytochemistry
• Humans
• Hyperthyroidism (diagnosis, etiology)
• Immunochemistry
• In Vitro Techniques
• Pituitary Neoplasms (blood, metabolism)
• RNA, Messenger (blood)
• Thyrotropin (blood, genetics, metabolism)
• Transcription, Genetic