Secretoglobins are a type of small, secreted proteins that are characterized by their unique structure, which includes two conserved cysteine residues and a pair of internal disulfide bonds. They are known to be involved in various biological processes, including immune response, inflammation, and tissue repair. Some secretoglobins have been found to bind and transport small hydrophobic molecules, such as steroids and lipids, while others may function as signaling molecules or have yet unidentified functions. They are expressed in a variety of tissues, including the respiratory, gastrointestinal, and reproductive tracts, as well as in various secretions such as tears, saliva, and milk.