Incorporated Cs137 and pathology of the thyroid gland

Y.I. Bandazhevsky

"Health effects of the Chernobyl accident : results of 15-years follow-up studies"

Conference: June 4 - 8, 2001, Kiev, Ukraine

Abstract published for the plenary session, Wednesday, June 6^th, 2001 :

"Stochastic effects of ionising radiation in exposed people (tumours, leukemia)

The incidence of thyroid diseases increased after the Chernobyl catastrophe. It is generally accepted that the enormous release of I131, a short-lived radionuclide, played a determinant role in initiating such processes.

It appears necessary to investigate the role of Cs137, a long-lived (30 years) omnipresent radionuclide, in the pathogenesis of auto-immune and neoplastic processes of the thyroid.

Method :

Researchers of the Gomel Medical Institute measured the Cs137 content of the thyroid glands, the muscle and the spleen of 52 children born after Chernobyl and 71 adults living in the contaminated regions. No thyroid disease was detected before death in these subjects.

Post-mortem histology of all thyroid glands was undertaken.

Results :

In children, the average Cs137 load in the thyroid gland reached 2.053.7(+-288.3) Bq/kg compared to 373.9(+-53.7) Bq/kg in adults.

These values were much higher than those measured in the skeletal muscle : 901.9 (+-237.7) Bq/kg in children compared to 195.9 (+-32.3) Bq/kg in adults. The thyroid concentrates significantly more Cs137 than muscle.

Histological examination of all thyroids showed dystrophy, necrosis of follicular cells, the connective tissue around the follicles showed infiltration with lymphocytes and histiocytes, with vascular changes, spotty fibrosis or diffuse sclerosis. Those important alterations may contribute to functional disorders, neoplasms and autoimmune reactions.

Discussion :

Cs137 in the epithelial cells alters metabolic processes, especially at mitochondrion level, inducing dystrophy and necrosis of these highly differentiated cells, and reduced secretion.

This radionuclide also alters the DNA of the thyroid cells, precipitating evolution toward neoplasm, in cells altered by I131, by inhibiting repair mechanisms.

The largest T-lymphocytes reservoir, the spleen had very high average Cs137 concentrations : 608.2(+-109.1) Bq/kg spleen in children and 195.5(+-24.7) Bq/kg in adults. T-Lymphocytes are not homogeneously affected by gamma rays : the suppressor T-lymphocytes are most susceptible. The loss of suppressor T-lymphocytes favours auto-immune reactions to thyroid antigens, released from Cs137 damaged cells; the risk of auto-immune thyroiditis increases.

Conclusion :

Incorporated Cs137 contributes to the pathogenesis of auto-immune and neoplastic thyroid diseases, in patients affected by Chernobyl fallout, even in children born years after the massive fallout of radioactive isotopes of iodine.

  Adress of the Authors :

Institute for Radioprotection "Belrad"

V. Khorushei 31a, 220002 Minsk, Belarus

 

Published in :    International Journal of Radiation Medicine 2001, 3 (1-2) p.10-11