Urological Health Penis Health Micropenis Overview Causes and Treatment of an Abnormally Small Penis By Jerry Kennard Jerry Kennard, PhD, is a psychologist and associate fellow of the British Psychological Society. Learn about our editorial process Jerry Kennard Medically reviewed by Medically reviewed by Matthew Wosnitzer, MD on June 24, 2020 twitter linkedin Matthew Wosnitzer, MD, is board-certified in urology. He is an attending physician at Yale New Haven Health System, Northeast Medical Group and teaches at the Frank Netter School of Medicine. Learn about our Medical Review Board Matthew Wosnitzer, MD on June 24, 2020 Print Table of Contents View All Table of Contents Symptoms Causes Diagnosis Treatment Coping Statistically, micropenis occurs in 0.6 percent of the population, making it a rare characteristic. The term is most commonly used when all other structures of the genitals, including the scrotum, testicles, and perineum, are "normal." During fetal development, deviations may occur as a result of a genetic aberration or be triggered by hormonal abnormalities. Micropenis Symptoms At birth, a penis that is less than 0.75 inch in length is considered a micropenis. As an adult, a flaccid penis less than 2.75 inches in length is considered a micropenis. An erect penis is considered a micropenis if it is less than 5 inches in length. Causes A micropenis develops during gestation. It will often be the only physiological abnormality noted in the pregnancy. One of the possible causes of this is the low production of human chorionic gonadotropin (hCG) during the early part of the pregnancy. This is a hormone that stimulates the developing testes to produce testosterone. After 14 weeks, penile growth falls under the influence of another hormone, known as luteinizing hormone (LH), which also stimulates testosterone in the so-called Leydig cells of the testicles. If the production of either or both of these fetal hormones is impeded, the child's penis length may be affected. Genetics may also play a role. While there is no single gene that causes a micropenis, the condition is commonly linked to such chromosomal disorders as androgen insensitivity syndrome (AIS), Klinefelter syndrome, Turner syndrome, and Down syndrome. There is also evidence that estrogen-based fertility drugs like diethylstilbestrol (DES) may cause smaller-than-normal penis size if taken during early pregnancy. While environmental pollutants are a less common cause, some research suggests that exposure to chlorinated pesticides during pregnancy may cause micropenis and other genital abnormalities in male babies. Diagnosis In newborns, it is vital that a doctor takes a proper measurement of the baby's penis when diagnosing micropenis. As opposed to a flaccid penis length (FPL), in which the penis is laid parallel to a ruler, a stretched penis length (SPL) should be used as it more closely correlates to the erect penis length in boys and men. For this, the doctor needs to hold a rigid ruler firmly against the pubis at a right angle. The penis is then held at the sides with calipers just below the glans (head) and stretched to its maximum length without pain. Newer syringe-like tools that can be placed over the penis and suction the organ to its fully stretched length are also available. Correctly identifying a micropenis in babies is crucial as it offers the opportunity for a potentially effective treatment. The doctor should also explore conditions commonly associated with a micropenis, including problems with the pituitary gland or hypothalamus. Defining Micropenis While an SPL of less than 1.9 centimeters is diagnostic of micropenis in full-term newborn, for older boys and men, a micropenis is characterized by penis length 2.5 standard deviations (SD) smaller than the mean average for the age. As a guideline, the Harriet Lane Handbook from John Hopkins University defines micropenis as follows: 6 to 12 months: less than 2.3 centimeters (0.9 inches)1 to 2 years: less than 2.6 centimeters (1.02 inches)2 to 3 years: less than 2.9 centimeters (1.14 inches)3 to 4 years: less than 3.3 centimeters (1.3 inches)4 to 5 years: less than 3.5 centimeters (1.38 inches)5 to 6 years: less than 3.8 centimeters (1.5 inches)6 to 7 years: less than 3.9 centimeters (1.54 inches)7 to 8 years: less than 3.7 centimeters (1.46 inches)8 to 9 years: less than 3.8 centimeters (1.5 inches)9 to 10 years: less than 3.8 centimeters (1.5 inches)10 to 11 years: less than 3.7 centimeters (1.46 inches)Adult: less than 9.3 centimeters (3.66 inches) The variations in mean penis size from age 7 are due to the differences in development as boys approach puberty. By puberty, it becomes far more difficult to define micropenis by centimeters alone; algorithmic calculations are needed until puberty is complete. Differential Diagnosis While the clinical definition of a micropenis seems to offer a definitive roadmap for diagnosis, that's not always the case. This is especially true in boys over the age of 8. In fact, most prepubescent boys brought in by their parents because of an underdeveloped penis rarely have a micropenis. In most cases, the boy is either experiencing delayed puberty, obesity (obscuring the penis length with excessive pubic fat), or he simply has a larger frame compared to an otherwise normal penis. In cases like these, the term "inconspicuous penis" may be more appropriately applied. It may be secondary to congenital conditions such as penoscrotal webbing (in which the scrotum extends up the underside of the penis, creating an indistinct junction between the two) and megaprepuce (in which the foreskin cannot retract and balloons abnormally). Treatment The treatment of micropenis will vary between children and adults. Given that the genitals of babies and toddlers are still developing, testosterone treatment can support penis growth, often significantly. Surgical options, while limited, may be explored in boys and men whose penises have reached their maximum growth. Depending on the treatment plan, the medical team may include a pediatrician, urologist, endocrinologist, geneticist, or psychologist. Testosterone Therapy A micropenis can be treated in infants and children with three monthly intramuscular (IM) injections of testosterone. Research has shown that one or two courses of three testosterone shots (25 to 50 milligrams) given in four-week intervals could increase the child's penis size to the reference range for his age. For a male baby with a micropenis, circumcision should be delayed until the testosterone therapy is completed. Generally speaking, the therapy is most effective in children under 3 but may benefit boys up to the age of 8. Gender Reassignment In the past, young children with a micropenis often underwent gender reassignment surgery, more in response to a general cultural discomfort with small penis size rather a real medical need. Today, that practice has largely subsided, with most experts questioning its wisdom given the potential benefit of testosterone therapy, the need for lifelong male-to-female hormone therapy in later life, and the lack of individual consent. If pursued, gender reassignment would generally be considered at a later age when the child has the ability to make an informed choice and has undergone extensive psychological evaluation. Penis Enlargement Surgery Some men with a micropenis will opt to undergo penis enlargement surgery (phalloplasty) with varying degrees of success. One such operation, called a suspensory ligament release, involves the detachment of the ligament that supports the penis during an erection. Doing so allows the penis to lie in an obtuse rather than an acute angle, creating the perception of greater length. Potential risks include nerve damage, loss of penile sensation, erectile dysfunction, and the retraction of the penis if scar tissue develops at the incision site. Other forms of phalloplasty, such as flap surgery (grafting skin from another of the body), are less commonly pursued because they carry a considerable risk of complications and may interfere with sexual function. Other techniques, such as silicone implants (prostheses), synthetic dermal fillers, and subcutaneous fat injections, are more likely to increase the girth rather than the length of the penis. Even if length gains are achieved, it would only affect the flaccid length, not the erect length, which would remain the same. There are also commercially marketed penis pumps and stretchers that have not demonstrated consistent results in delivering gains in penis length. If achieved, they tend to be modest at best. These devices are intended for males with erectile dysfunction—an entirely separate concern. Coping From a practical standpoint, micropenis may complicate urination by making it difficult to direct the stream. Many men will simply compensate for this by sitting on the toilet when urinating. Reproduction On a more significant note, penis length of fewer than 2 inches is associated with a lower likelihood of conception. Moreover, some men with a micropenis will have a low sperm count as the result of an underlying pituitary disorder. In such cases, assisted reproductive techniques are available to significantly improve one's chances of conceiving. Emotional While there are treatments that may enhance penis size, the reality is that some individuals will have a smaller-than-normal penis. While some people assume that this will cause inherent psychological harm, those beliefs are more reflective of our cultural attitudes about penis size rather than the person's individual experience. In fact, long-term research has shown that men with micropenises are no different in how they view their masculine self-image compared to men of average or above-average penis size. Sexual Micropenis has not been shown to interfere with a man's libido, sexual function, sexual satisfaction, ability to achieve an erection, or the ability to forge mutually gratifying sexual relationships. Was this page helpful? Thanks for your feedback! Sign up for our Health Tip of the Day newsletter, and receive daily tips that will help you live your healthiest life. Sign Up You're in! Thank you, {{form.email}}, for signing up. There was an error. Please try again. What are your concerns? Other Inaccurate Hard to Understand Submit Article Sources Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Cleveland Clinic. Micropenis. 2018. Hatipoğlu N, Kurtoğlu S. Micropenis: etiology, diagnosis and treatment approaches. J Clin Res Pediatr Endocrinol. 2013;5(4):217-23. doi:10.4274/Jcrpe.1135 Walia R, Singla M, Vaiphei K, Kumar S, Bhansali A. Disorders of sex development: a study of 194 cases. Endocr Connect. 2018;7(2):364-371. doi:10.1530/EC-18-0022 Mahawong P, Sinclair A, Li Y, et al. Prenatal diethylstilbestrol induces malformation of the external genitalia of male and female mice and persistent second-generation developmental abnormalities of the external genitalia in two mouse strains. Differentiation. 2014;88(2-3):51-69. doi:10.1016/j.diff.2014.09.005 Street ME, Angelini S, Bernasconi S, et al. Current Knowledge on Endocrine Disrupting Chemicals (EDCs) from Animal Biology to Humans, from Pregnancy to Adulthood: Highlights from a National Italian Meeting. Int J Mol Sci. 2018;19(6):1647. doi:10.3390/ijms19061647 Srinivasan AK, Palmer LS, Palmer JS. Inconspicuous penis. ScientificWorldJournal. 2011;11:2559-64. doi:10.1100/2011/238519 Jones HW, Park IJ, Rock JA. Technique of surgical sex reassignment for micropenis and allied conditions. Am J Obstet Gynecol. 1978;132(8):870-7. Campbell J, Gillis J. A review of penile elongation surgery. Transl Androl Urol. 2017;6(1):69-78. doi:10.21037/tau.2016.11.19 Tuğ E, Güntekin ergün S, Ergün MA, Dilek FN, Perçin EF. The relation between isolated micropenis in childhood with CAG and GGN repeat polymorphisms in the androgen receptor gene. Turk J Med Sci. 2018;48(2):430-434. doi:10.3906/sag-1710-183 Tsang, S. When size matters: A clinical review of pathological micropenis. J Ped Health Care. 2010;24(4):231-40. doi:10.1016/j.pedhc.2009.05.001 Lee PA, Houk CP. Outcome studies among men with micropenis. J Pediatr Endocrinol Metab. 2004;17(8):1043-53. Additional Reading Gaspari, L.; Paris, F.; Jandel, C. et al. Prenatal environmental risk factors for genital malformations in a population of 1442 French male newborns: a nested case-control study. Hum Reproduction. 2011;26(11):3155-62. DOI: 10.1093/humrep/der283. John Hopkins Hospital; Kahl, L.; and Hughes, H. (2017) The Harriet Lane Handbook: Mobile Medicine Series (21st Edition). New York, New York: Elsevier. ISBN-13:978-0323399555 Srinvasan, A.; Palmer, L.; and Palmer, J. Inconspicuous Penis. Sci World J. 2011;11:2559-64. DOI: 10.1100/2011/238519.