The TSH cyclic AMP cascade in the control of thyroid cell proliferation: the story of a concept.

Thyrotropin stimulates the growth and proliferation of thyroid cells in vivo. Starting in the 1970, we have progressively shown that these effects could be reproduced in vitro in dog thyroid cells in primary culture. They are accompanied by the expression of differentiation. All the effects of thyrotropin are mediated by the cyclic AMP cascade. The best argument that this concept applies in vivo is the generation of hyperfunctioning adenoma involving the whole gland in transgenic mice expressing the constitutively active adenosine A2 receptor in the thyroid.