Microorchidism is the medical term used to describe a genetic disorder found in males where a subject has abnormally small testes. The condition is associated with (and often secondary to) a number of other genetic disorders, including Klinefelter's Syndrome

Klinefelter's syndrome

Klinefelter syndrome, 46/47, XXY, or XXY syndrome is a condition in which human males have an extra X chromosome. While females have an XX chromosomal makeup, and males an XY, affected individuals have at least two X chromosomes and at least one Y chromosome...

 and Prader-Willi syndrome, as well as other multiple malformation disorders. The degree of abnormality (or otherwise) of the testes can be determined by the use of an orchidometer

Orchidometer

An orchidometer is a medical instrument used to measure the volume of the testicles.The orchidometer was introduced in 1966 by pediatric endocrinologist Prof. Dr. Dr. hc. Andrea Prader of the University of Zurich. It consists of a string of twelve numbered wooden or plastic beads of increasing...

. In addition, Microorchidism may also occur as a result of shrinkage or atrophy

Atrophy

Atrophy is the partial or complete wasting away of a part of the body. Causes of atrophy include mutations , poor nourishment, poor circulation, loss of hormonal support, loss of nerve supply to the target organ, disuse or lack of exercise or disease intrinsic to the tissue itself...

 of the testis due to infections like mumps

Mumps

Mumps is a viral disease of the human species, caused by the mumps virus. Before the development of vaccination and the introduction of a vaccine, it was a common childhood disease worldwide...

.