CTRP (C1q/TNF-related proteins) proteins constitute a conserved, structurally related family of 15 members. Every CTRP protein contains a signal peptide, an N-terminal domain with one or more conserved Cysteines, a collagen-like domain, and a C-terminal globular C1q domain. All are trimeric, and can also form high order oligomers. CTRP proteins are secreted and detected in the circulation. Receptors include members of the brain-specific angiogenesis inhibitor (BAI) subfamily of adhesion G-protein-coupled receptors.

These relatively unknown proteins show great potential for new scientific discovery with studies indicating involvement with cardiovascular disorders, insulin-sensitization, inflammation, and angiogenesis.