Micropenis. I. Criteria, etiologies and classification.

A micropenis is an abnormally small penis with a normal configuration. This finding constitues a sign not a diagnosis. The etiologies may be classified as hypogonadotropic hypogonadism, primary hypogonadism, androgen insensitivity, or idiopathic; among 45 patients, the respective percentages in these categories were 31, 24, 2 and 7% with 36% as yet undiagnosed. Various clinical syndromes may include a micropenis and can be classified in one of the etiologic categories. This paper provides the criteria for determining the presence of a micropenis. A phallic length which is 2.5 or more standard deviations below the mean should be considered as abnormal; for an infant of 0 to 5 months of age, the lower limit is 1.9 cm. The technique of penile measurement, determination of etiology, guidelines for sex of rearing and psychologic, surgical and medical management are discussed.