False pregnancy or hysterical pregnancy, most commonly termed pseudocyesis in humans and pseudopregnancy in other mammals, is the appearance of clinical and/or subclinical signs and symptoms associated with pregnancy when the organism is not actually pregnant. Clinically, false pregnancy is most common in veterinary medicine (particularly in dogs and mice). False pregnancy in humans is less common, and may sometimes be purely psychological. It is generally estimated that false pregnancy is caused due to changes in the endocrine system of the body, leading to the secretion of hormones which translate into physical changes similar to those during pregnancy.