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Thyroid growth and function are increased in mice in which the growth-promoting substance, insulin-like growth factor-I, and its receptor are expressed in thyroid tissue

(March 2002)

The background of the study. Insulin-like growth factor-I (IGF-I), acting via its receptor on cells, stimulates the growth of many tissues. In this study the gene for IGF-I, the gene for the IGF-I receptor, and both genes, were introduced into thyroid tissue of mice to determine if thyroid growth and function were affected.

How the study was done. Transgenic mice were produced by injecting portions of the human IGF-I gene or the IGF-I receptor gene into fertilized mouse eggs. Mice carrying each gene were bred together to obtain mice bearing both genes. Expression of the two genes was verified by detection of the gene products in thyroid tissue of these mice, but not in thyroid tissue from normal mice.

The results of the study. The body weight and behavior of the transgenic mice were similar to that of normal mice. The weight of the thyroid glands and the thyroid function were higher in the mice with both transgenes.

The conclusions of the study. In mice, insertion of the genes for IGF-I and its receptor in thyroid tissue results in increased thyroid growth and function. Increases in these two substances in thyroid tissue could play a role in the causation of goiter in humans.

The original article. Clement S, Refetoff S, Robaye B, Dumont JE, Schurmans S. Low TSH requirement and goiter in transgenic mice overexpressing IGF-I and IGF-I receptor in the thyroid gland. Endocrinology 2001;142:5131-9.