High affinity relaxin receptors, polypeptide compositions related thereto, as well as nucleotide compositions encoding the same, are provided. These proteins, herein termed LGR7 and LGR8, are orphan leucine-repeat-containing, G protein-coupled receptors. These receptors have a wide and a unique tissue expression pattern. The receptors, particularly soluble fragments thereof, are useful as therapeutic agents capable of inhibiting the action of relaxin and InsL3. The receptors and fragments thereof also find use in the screening and design of relaxin agonists and antagonists. Conditions treatable with relaxin agonists or antagonists include prevention or induction of labor, treatment of endometriosis, treatment of skin conditions such as scleroderma that require collagen or extracellular matrix remodelling. Additionally, relaxin has been implicated in the dilation of blood vessels' smooth muscle cells directly and through release of nitric oxide and atrial natriuretic peptide. Relaxin has also been used in the treatment of severe chronic pain, particularly pain arising from stretching, swelling, or dislocation of tissues.