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  • Title: Thyroid-stimulating hormone activates phospholipase C in normal and neoplastic thyroid tissue.
    Author: Shaver JK, Tezelman S, Siperstein AE, Duh QY, Clark OH.
    Journal: Surgery; 1993 Dec; 114(6):1064-9. PubMed ID: 8256209.
    Abstract:
    BACKGROUND: Thyroid-stimulating hormone (TSH) stimulates thyroid growth through two signal transduction pathways: the G protein-adenylate cyclase system and the G protein-phospholipase C (PLC) system. The adenylate cyclase system has been studied extensively, but there is little information available concerning PLC activity in thyroid neoplasms. METHODS: Human thyroid membranes were incubated for 30 minutes at 37 degrees C in the presence or absence of bovine TSH (300 mU/ml). PLC activity was assayed by liberation of inositol phosphates from the enzymatic hydrolysis of tritiated phosphatidylinositol bisphosphate. Fifty-six tissues were assayed (normal, 23; multinodular goiter, 5; follicular adenoma, 9; and differentiated thyroid cancer, 19 [9 low risk and 10 high risk]). RESULTS: TSH significantly increased PLC activity in normal, benign, and most malignant thyroid neoplasms. Although there were no differences in basal or TSH-stimulated PLC activity between the groups of normal thyroid, multinodular goiter, follicular adenoma, or the cancers, one half of the high-risk cancers had an aberrant PLC response. CONCLUSIONS: This is the first demonstration that TSH stimulates PLC activity in normal and neoplastic human thyroid tissue. Aberrant TSH-stimulated PLC activity was present in half of the aggressive thyroid neoplasms.
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