IGF1 and hypothyroidism: The direct renal hemodynamic effects of hypothyroidism include impaired vasodilation [15], decreased expression of vasodilators, such as vascular endothelial growth factor and insulin-like growth factor-1 [16], increased adenosine [8, 17, 18], and contraction of afferent arterioles [17] due to the tubulo-glomerular feedback mechanism.