PDE5A and thyroid cancer: We have recently demonstrated the overexpression of phosphodiesterase-5 (PDE5) that occurs, the enzyme which specifically regulates the intracellular levels of cGMP, in a series of thyroid carcinomas; also, the inhibition of PDE5 by sildenafil (SIL) or tadalafil (TAD) determined a block in the proliferation of thyroid cancer cells in culture, suggesting that specific inhibitors of PDE5 may be proposed for the treatment of these tumors [10].