THBS1 and hydrops fetalis: Furthermore, we asked whether different HF types in FPHL patients exhibit differences in perifollicular vascularization and angiogenesis-associated growth factors, i.e., vascular growth factor (VEGF) and trombospondin-1 (TSP-1) using quantitative (immuno-)histomorphometry in biopsies from parietal and/or occipital scalp given that nutrient supply and hair growth depend on adequate angiogenesis [44].