Clitoromegaly, or abnormal enlargement of the clitoris, is most commonly caused by excess androgens (male-type hormones) in the body. These androgens can come from a genetic condition present at birth, a hormone-producing tumor, a medication, or rarely a structural growth like a benign nerve tumor. In newborns, a clitoral length greater than 6.5 mm is generally considered enlarged, while values at or above 8 mm typically prompt further investigation. In adults, a clitoral index (length multiplied by width of the glans) greater than 35 square millimeters is a commonly used threshold.
Congenital Adrenal Hyperplasia
Congenital adrenal hyperplasia (CAH) is the single most common cause of clitoromegaly in newborns. It’s a group of inherited conditions where genetic mutations disable enzymes the adrenal glands need to produce cortisol. When cortisol production is blocked, the brain’s pituitary gland keeps sending signals to the adrenals to work harder. The adrenals grow larger in response, and the backed-up hormone production gets rerouted into making androgens instead of cortisol.
About 95% of CAH cases involve a deficiency of one specific enzyme (21-hydroxylase). With this enzyme missing or impaired, the adrenals can’t complete the final steps of making cortisol or aldosterone. The raw materials pile up and get shunted toward androgen production. In a female fetus, those excess androgens cause varying degrees of genital virilization during development, ranging from mild clitoral enlargement with no other changes to more significant fusion of the labia and repositioning of the urethral opening.
Doctors classify the degree of virilization using a five-stage scale developed by Prader. Stage I is clitoral enlargement alone, with no labial fusion. By stage III, the clitoris is more significantly enlarged with near-complete labial fusion. Stage V, the most extreme, involves a fully penile-appearing clitoris with a urethral opening at the tip and labia that resemble a scrotum. Most cases of CAH fall somewhere in the earlier stages.
Polycystic Ovary Syndrome
PCOS is a far more common hormonal condition than CAH, but it causes clitoromegaly much less frequently. Only about 2% to 3% of people with PCOS develop a noticeable degree of clitoral enlargement. In PCOS, elevated levels of luteinizing hormone and insulin-like growth factor stimulate the ovaries and adrenal glands to overproduce androgens. Those same androgens responsible for acne, excess hair growth, and hair thinning in PCOS can, over time, cause the clitoral tissue to enlarge. The degree is typically mild compared to what’s seen with CAH or androgen-secreting tumors.
Androgen-Secreting Tumors
Tumors in the ovaries or adrenal glands that produce androgens are rare, but they tend to cause rapid and dramatic changes. Unlike PCOS, where symptoms develop gradually over months or years, androgen-secreting tumors often cause sudden-onset virilization: fast-progressing hair growth, deepening of the voice, loss of typical female body contour, and clitoral enlargement that may develop over weeks to months.
The most common virilizing ovarian tumors are Sertoli-Leydig cell tumors, which account for about 0.5% of all ovarian tumors. Adrenal tumors can produce similar effects. A testosterone level above 350 ng/dL raises suspicion for an ovarian tumor, while very high levels of the adrenal androgen DHEAS (above 700 mg/dL) point toward an adrenal source. The speed of symptom progression is one of the most important clues distinguishing a tumor from other causes.
Medications and External Exposure
Exogenous androgens, meaning hormones entering the body from an outside source, can directly stimulate clitoral growth. This includes anabolic steroids, testosterone therapy, and even accidental skin-to-skin transfer of testosterone gel from a partner or parent. The FDA flagged unintended virilization from testosterone gel transfer as a recognized risk in 2009, after cases emerged of children developing virilization symptoms from contact with adults using topical testosterone.
The good news is that clitoral enlargement from external androgen exposure can sometimes reverse once the source is removed. Case reports show mixed results: some people see significant improvement after discontinuing the offending agent, while others retain some degree of enlargement even after hormone levels normalize. Bone age advancement, another effect of androgen exposure in children, may not reverse at all.
Differences of Sex Development
Clitoromegaly can be one feature of a broader difference of sex development (DSD), a group of conditions where chromosomal, gonadal, or anatomical sex doesn’t follow typical patterns. Beyond CAH, which itself falls under the DSD umbrella, other conditions in this category include 5-alpha-reductase deficiency and androgen insensitivity syndrome. In partial androgen insensitivity, for instance, the body’s cells respond incompletely to androgens, which can result in a range of genital appearances including clitoral enlargement.
Symptoms associated with DSDs vary widely and can include ambiguous genitalia at birth, delayed or absent puberty, unexpected changes during puberty, or the discovery of unexpected internal anatomy (such as undescended testes in someone raised female). Many of these conditions aren’t identified until puberty, when expected development doesn’t occur or unexpected virilization begins.
Neurofibromas and Other Structural Causes
In rare cases, clitoromegaly has nothing to do with hormones at all. Neurofibromatosis type 1 (NF1), a genetic condition that causes benign nerve tumors, can produce growths called plexiform neurofibromas in the genital area. Genital involvement in NF1 is extremely rare, occurring in about 0.65% of affected individuals, but when it does happen, the clitoris is the most commonly reported site. One documented case involved a soft-tissue mass centered on the clitoris measuring over 9 centimeters, confirmed as a plexiform neurofibroma in a patient with characteristic skin findings of NF1.
Other non-hormonal structural causes include cysts and hemangiomas (tangles of blood vessels) in the clitoral region. These are exceedingly uncommon but important to consider because the workup and treatment differ completely from hormone-driven causes.
How the Cause Is Identified
Because the causes range from common hormonal conditions to rare tumors and genetic syndromes, identifying the underlying reason for clitoromegaly typically involves a layered approach. Blood tests measure hormone levels: testosterone, DHEAS, and 17-hydroxyprogesterone (which is elevated in CAH). The ratio of luteinizing hormone to follicle-stimulating hormone can help identify PCOS. If those initial results point toward a tumor, imaging of the ovaries and adrenal glands follows.
For newborns with ambiguous genitalia, the evaluation is more extensive and may include chromosomal analysis (karyotyping), additional hormone stimulation tests, and imaging of internal reproductive structures. The goal is to distinguish between conditions that need urgent medical treatment, like the salt-wasting form of CAH where aldosterone deficiency can cause a life-threatening electrolyte crisis, and conditions that can be monitored over time.