CAPS1 is a 189 amino acid cytoplasmic protein that contains four EF-hand domains, which serve as calcium-binding sites, and was first identified in canine thyroid. Interestingly, CAPS1 is much less abundant in humans than in canines. Synthesis and phosphorylation of CAPS1 is upregulated by cAMP-agonists in thyrocytes. CAPS1 likely functions in the regulation of ionic transport and may be involved in cross-signaling between cAMP and Ca(+2)-phophatidylinositol cascades. In addition to thyriod, CAPS1 is expressed in brain, salivary glands and lung. Expression of CAPS1 is increased in endometrial cancer and prognosis seems to be dependent on the level of CAPS1 expression, indicating that CAPS1 may be an appropriate prognostic marker for patient survival.