 The thyroid gland requires a unique vasculature structure to properly function. This structure includes endothelial fenestry, which are small openings in the endothelium of blood vessels. The thyroid gland's ability to maintain this structure is dependent on a complex signaling pathway involving VegFa and its receptor VEGFR2. When thyrotropin levels increase, VegFa and VEGFR2 are expressed at higher levels, resulting in increased endothelial fenestry and normal thyroid function, blocking either VegFa or VEGFR2 results in reduced endothelial fenestry and decreased thyroid weight, suggesting that this signaling pathway plays a key role in thyroid development and function. This article was authored by John Yoke Jang, Sun Yong Choi, in Tate Park and others.