SPRY4 encodes a negative regulator of receptor tyrosine kinase (RTK) signaling that suppresses insulin receptor and EGFR-dependent MAPK activation, primarily by impairing GTP-Ras formation. The protein also inhibits integrin-mediated cell spreading through TESK1-mediated cofilin phosphorylation. Beyond its canonical RTK antagonism, SPRY4 modulates vascular smooth muscle cell phenotype via the Akt/FoxO/myocardin pathway, with Spry4 suppressing differentiation markers in this context. Pathogenic SPRY4 variants contribute to congenital hypogonadotropic hypogonadism and Kallmann syndrome, where 14 individuals from a cohort of 386 carried mutations in FGF8 synexpression group genes 1. Recently, a heterozygous missense variant was identified in a female infertility case characterized by reduced oocyte potential and early embryonic arrest, with functional studies showing the variant disrupts mitochondrial redox homeostasis in oocytes 2. In steroid-induced osteonecrosis of the femoral head, exosomal SPRY4 from adipogenic bone marrow mesenchymal stem cells impairs angiogenesis by suppressing the PTPRB/TIE2/PI3K axis; pharmacological inhibition of PI3K or modulation of PTPRB signaling with compounds such as AKB9778 reversed pathological manifestations 3. In testicular germ cell tumors, SPRY4 expression is elevated and knockdown reduces cell growth and Akt phosphorylation, suggesting oncogenic activity in this context 4, whereas its intronic long noncoding RNA SPRY4-IT1 associates with poor overall survival across multiple cancer types 5.