J.Jpn. Surg. Soc.. 90(12): 2000-2007, 1989

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Original article

PROMOTING EFFECT OF ENDOGENOUS TSH ON CARCINOGENESIS OF RAT THYROID TRANSPLANTED INTO THE SPLEEN

In an attempt to clarify a modifying effect of TSH on thyroid tumorigenesis, we carried out intrasplenic thyroid autotransplantation in rats treated with a thyroid carcinogen, diisopropanolnitrosamine (DIPN). Experiments comprised 3 groups of Wistar male rats: Group I (effective no., 15), total thyroidectomy plus hemithyroid transplantation 2 weeks after subcutaneous injection of DIPN at a dose of 2.4g/kg BW; group II (effective no., 22), DIPN alone;group III (effective no., 18), transplantation alone. The thyroid lesions of all rats at week 28 were examined by histopathology and enzyme histochemistry for γ-glutamyl transpeptidase (GGT).
Periodical radioimmunoassay for serum T₃, T₄ and TSH revealed low levels of T₃ ＆ T₄ for at least 10weeks and increased level of TSH until week 18 after the transplantation. Altered foci (AF) occurred in 36% and 6% of rats in group I and group II, respectively, whereas neoplastic nodules (NN) were found in 53% of rats only in group I. Both AF and NN displayed a positive reaction for GGT which was considered to be a useful marker for preneoplastic and neoplastic thyroid lesions.
The present data are indicative that increased serum level of TSH for a significant period may exert apromoting effect on thyroid tumorigenesis.

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