Virilization is the development of physical traits typically associated with male sex hormones, occurring in someone who would not otherwise develop them. It can happen to a female infant in the womb, a young girl before puberty, an adult woman, or even a prepubertal boy exposed to androgens too early. The signs range from excess body hair and acne to voice deepening, clitoral enlargement, and changes in muscle mass and fat distribution. When androgen levels climb to roughly three to five times above normal for age and sex, the effects move beyond mild “hyperandrogenism” into frank virilization, with changes that can reshape the body and, in some cases, prove irreversible.
How Androgens Drive the Process
The biology behind virilization centers on androgens, the family of hormones that includes testosterone and its more potent derivative, dihydrotestosterone (DHT). During typical fetal development, the testes produce testosterone, which is then converted to DHT in genital skin. This sequence is what drives the formation of male external genitalia in the womb.1BJU International. The virilized female: endocrine background In the adrenal glands, the precursor hormone dehydroepiandrosterone (DHEA) feeds into the same pathway: it can be converted into testosterone and then DHT, meaning the adrenals are a second factory capable of producing virilizing hormones.2PubMed Central. Alternative pathway androgen biosynthesis and human fetal female virilization
Skin cells themselves carry the full set of enzymes needed to manufacture androgens locally, which is why skin-related symptoms like acne, oily skin, excess hair growth, and scalp hair thinning are often the first visible signs of androgen excess.3PubMed. Androgen action on human skin — from basic research to clinical significance The ovaries, adrenal glands, and peripheral tissues like skin all talk to one another hormonally, so a problem in any one of these compartments can tip the balance.
Congenital Adrenal Hyperplasia
The single most common genetic cause of virilization is congenital adrenal hyperplasia (CAH), specifically the form caused by a deficiency of the enzyme 21-hydroxylase. This is an inherited condition passed down from both parents. The enzyme deficiency disrupts the adrenal gland’s ability to make cortisol, and the body’s attempt to compensate shunts steroid precursors into androgen production instead. The excess androgens, particularly testosterone, then cause genital ambiguity in affected female newborns.4JCI Insight. Ontogeny of adrenal steroid biosynthesis: why girls will be girls In its most severe “classic” form, the virilization is progressive and can produce external genitalia that look partially or fully masculine at birth.5Global Library of Women’s Medicine. Congenital Adrenal Hyperplasia: Female Pseudohermaphroditism and Virilization
Classic CAH comes in two subtypes: a “salt-wasting” form, which also disrupts the body’s ability to retain sodium and can cause life-threatening crises in newborns, and a “simple virilizing” form where cortisol production is impaired but salt balance stays intact. The simple virilizing form may sometimes escape newborn screening and not be caught until later childhood or even adolescence, when progressive signs like rapid growth, early pubic hair, or deepening voice prompt evaluation.6Annals of Medicine and Surgery. A rare case report about a congenital adrenal hyperplasia by 21-hydroxylase lock in its pure virilizing form discovered in adolescence
There is also a milder “non-classic” form of 21-hydroxylase deficiency, which is far more common. People with non-classic CAH make enough cortisol to avoid a crisis, but still overproduce adrenal androgens. Their symptoms overlap heavily with polycystic ovary syndrome (PCOS): irregular periods, acne, and excess hair growth. In fact, the clinical picture is similar enough that non-classic CAH is sometimes mistaken for PCOS and vice versa.7PubMed Central. Nonclassic Congenital Adrenal Hyperplasia: What Do Endocrinologists Need to Know?
Virilization That Appears at Puberty
One of the more striking presentations involves individuals born with an enzyme deficiency called 5-alpha reductase type 2 deficiency. These individuals are genetically male (XY chromosomes) but are born with external genitalia that appear female or ambiguous, because the enzyme needed to convert testosterone to DHT in genital skin is missing during fetal development. They are typically raised as girls. Then, at puberty, the surge of testosterone causes masculinization: the voice deepens, muscle mass increases, the phallus enlarges, and the body takes on a more masculine shape. A well-documented pedigree in Southern Lebanon described eight individuals who were reared as girls until puberty triggered masculinization, after which several changed their gender role.8The Journal of Clinical Endocrinology & Metabolism. Clinical, biochemical, and genetic findings in a large pedigree of male and female patients with 5 alpha-reductase 2 deficiency
This condition is rare globally but clusters in certain communities where consanguineous marriage is more common, increasing the chances that both parents carry the same recessive gene. It illustrates how virilization is not always a matter of “too much androgen” but sometimes about timing: the same hormones that failed to act in utero can act powerfully once puberty amplifies them.
Androgen-Secreting Tumors
When virilization appears suddenly in an adult woman and progresses rapidly over weeks or months, the concern shifts from genetic conditions to tumors. Both the ovaries and the adrenal glands can develop androgen-secreting growths. Among ovarian tumors, Sertoli-Leydig cell tumors are a well-known culprit; their presence should be suspected when a woman develops signs of virilization alongside a pelvic mass.9International Journal of Surgery Case Reports. Ovarian Sertoli-Leydig tumor: A tricky tumor case report On the adrenal side, adrenocortical carcinomas are a rarer but more dangerous possibility. Roughly 60 percent of adrenal tumors are hormonally active, and those that secrete androgens can cause rapid virilization.10PubMed Central. A case of androgen-secreting adrenal carcinoma with non-classical congenital adrenal hyperplasia
The critical red flag is speed. Hirsutism (excess body and facial hair) affects up to about a quarter of reproductive-age women, and PCOS is by far the most common cause. But when hyperandrogenic symptoms develop fast and keep worsening, or when total testosterone levels are more than three times the upper limit of normal, an androgen-producing tumor moves to the top of the differential.11PubMed Central. Total testosterone levels are often more than three times elevated in patients with androgen-secreting tumours These tumors can be malignant and usually require surgery, so catching them early matters.
Anabolic Steroids and Accidental Testosterone Exposure
A growing source of virilization is exogenous androgens: steroids taken deliberately, or testosterone absorbed inadvertently from someone else’s medication. In women who use anabolic-androgenic steroids (AAS), prolonged use or high doses can produce voice deepening, clitoral enlargement, menstrual disruption, mood changes, and cardiovascular complications.12PubMed Central. Impacts of Anabolic-androgenic steroid supplementation on female health and offspring: Mechanisms, side effects, and medical perspectives Qualitative research with women who have used AAS reveals that many find the masculinizing effects difficult to process emotionally. Some changes, particularly to the voice and clitoris, do not fully reverse after stopping, and this can affect self-esteem, social life, and sexual function.13PubMed. Anabolic-androgenic steroid use among women – A qualitative study on experiences of masculinizing, gonadal and sexual effects
Perhaps more surprising is the phenomenon of secondary transfer from testosterone gel. Men prescribed topical testosterone can inadvertently pass the hormone to children or partners through skin-to-skin contact. The FDA has issued warnings about this risk after reports of virilization in children exposed to a parent’s testosterone gel.14PubMed Central. Prenatal virilization associated with paternal testosterone gel therapy Case reports describe prepubertal children developing pubic hair, genital enlargement, and accelerated growth after passive transfer from a father’s topical testosterone.15PubMed. Virilization in two pre-pubertal children exposed to topical androgen This is entirely preventable with proper hand-washing and covering the application site, but it remains an underappreciated risk.
What Virilization Looks and Sounds Like
The physical signs of virilization exist on a spectrum from mild to severe. On the milder end sit oily skin, acne, and increased hair growth on the face, chest, abdomen, and back. These are the features most commonly shared with PCOS and non-classic CAH, and they respond to lowering androgen levels or blocking androgen receptors.
As androgen exposure increases in dose and duration, more pronounced changes appear:
- Voice deepening: Androgens cause the vocal folds to thicken, which lowers pitch. In adult women exposed to exogenous testosterone, the vocal folds gain mass without the surrounding cartilage growing, which differs from typical male puberty and can produce voice instability alongside the lower pitch.16PubMed Central. Longitudinal Case Study of Transgender Voice Changes under Testosterone Hormone Therapy
- Clitoral enlargement: Androgen exposure directly stimulates clitoral growth, whether the source is endogenous overproduction or external contact with testosterone products.
- Male-pattern hair loss: Scalp hair may thin at the temples and crown, following the same pattern seen in men with androgenetic alopecia.
- Menstrual disruption: Excess androgens interfere with ovulation, leading to irregular or absent periods.
- Increased muscle mass and changed fat distribution: The body shifts toward a more masculine body composition, with greater lean mass and less subcutaneous fat on the hips and thighs.
Voice change deserves special attention because it is one of the effects most likely to be permanent. A scoping review of androgen-related voice changes in cisgender women found that the severity depends on dose, duration, and delivery route. Transdermal formulations like patches and creams tended to produce minimal voice effects, while intramuscular injections of testosterone or anabolic steroids were associated with meaningful pitch lowering, voice instability, and structural changes in the vocal folds. Premenopausal women appeared more susceptible to these effects than postmenopausal women.17Laryngoscope. Voice Change as a Result of Androgen Supplementation in Cisgender Women: A Scoping Review Another case series confirmed that even when androgen therapy is stopped, voice changes may persist indefinitely. Voice therapy can help with vocal quality and control, but the fundamental pitch reduction often does not fully reverse.18PubMed. Voice Change Following Testosterone Supplementation in Women: A Multi-Institutional Case Series
Sorting Out the Cause
When a clinician evaluates someone for virilization, the first step is usually measuring serum testosterone and related hormones like DHEA-sulfate (DHEAS), which tends to be elevated in adrenal-driven causes but normal in ovarian ones. The speed at which symptoms developed is a crucial part of the history. A woman who developed worsening hirsutism over several years is much more likely to have PCOS or non-classic CAH than someone whose symptoms appeared within a few months, which raises the alarm for a tumor.19PubMed Central. Differentiating Polycystic Ovary Syndrome from Adrenal Disorders
Imaging comes next when the hormone profile is suspicious. Ultrasound is usually the first-line tool for the ovaries, and CT or MRI for the adrenal glands. Sometimes the picture is not straightforward: in one reported case, a woman with markedly elevated testosterone had normal-looking ovaries on initial ultrasound, but a Doppler ultrasound later revealed a small solid mass in one ovary. Her DHEAS was normal, which helped point away from the adrenal nodule also seen on CT and toward the ovary as the androgen source.20PubMed Central. Virilising ovarian tumour in a woman with an adrenal nodule Even in children, imaging with CT and ultrasound has been used to accurately locate small adrenal tumors causing virilization.21American Journal of Diseases of Children. Virilizing Adrenal Tumor in a 3-Year-Old Girl: Diagnosis by Computed Tomographic Scan and Ultrasound
In practice, clinicians also use hormonal suppression tests. A dexamethasone suppression test can help distinguish adrenal from ovarian androgen sources: if a short course of dexamethasone (which suppresses the adrenal gland) brings testosterone levels down, the adrenals are the likely origin. If testosterone stays elevated, the ovaries become the primary suspect.
When Virilization Is the Goal
For transgender men and some nonbinary individuals, virilization is not an unwanted side effect but the entire point of hormone therapy. Gender-affirming testosterone treatment deliberately induces many of the same changes discussed above: voice deepening, facial hair growth, redistribution of body fat, increased muscle mass, cessation of menstruation, and clitoral growth. Research has shown that even low-dose testosterone is sufficient to increase lean body mass in trans men over the long term, and that higher doses can speed the process along.22PubMed. Trans men can achieve adequate muscular development through low-dose testosterone therapy: A long-term study on body composition changes
Facial bone structure also shifts subtly. Three-dimensional scanning of trans men on testosterone therapy showed measurable changes in the cheek and jaw regions by 12 months, with the cheeks moving slightly inward and backward, contributing to a more angular facial appearance.23The Journal of Sexual Medicine. Gender-Affirming Hormone Treatment Induces Facial Feminization in Transwomen and Masculinization in Transmen: Quantification by 3D Scanning and Patient-Reported Outcome Measures These changes develop gradually, and the degree of virilization varies between individuals based on genetics, receptor sensitivity, and dose.
The timeline matters here too. Voice deepening typically begins within the first three to six months and progresses over one to two years. Body hair and facial hair growth is slower, often taking several years to reach its full extent. Menstrual cessation usually happens within the first six months of adequate dosing. Understanding this timeline helps set realistic expectations for patients.
What Reverses and What Does Not
One of the most important practical questions around virilization is which changes are reversible once the androgen source is removed. The answer depends on which tissues were affected and for how long.
Changes that tend to reverse when androgen levels normalize include acne, oily skin, menstrual irregularity, and to some extent the redistribution of body fat. Muscle mass gained under androgen influence will gradually decrease without ongoing hormonal support. Scalp hair thinning may partially recover, though regrowth varies widely between individuals.
Changes that tend to be permanent or very difficult to reverse include voice deepening, clitoral enlargement, and male-pattern facial and body hair growth. The vocal folds, once thickened by androgens, do not thin out when testosterone drops. Voice therapy can improve vocal control and quality, but the fundamental frequency generally stays lower. Similarly, once terminal (coarse, dark) hair follicles have been activated on the face, they tend to keep producing hair even after androgens normalize, though the rate of growth may slow. Electrolysis or laser treatment is usually needed for more complete removal.
For virilized female newborns with CAH, surgical options exist to address genital ambiguity, though the timing and approach to genital surgery in infants has become a subject of significant ethical discussion in recent years. Many clinicians and patient advocacy groups now recommend delaying surgery until the individual can participate in the decision, unless there is a functional medical need.
The PCOS Overlap and Why It Causes Confusion
PCOS is the most common hormonal disorder in reproductive-age women, and mild androgen excess is one of its defining features. Most women with PCOS experience hirsutism, acne, or thinning hair, but not the full-blown virilization described above. The distinction matters because the workup and treatment paths diverge sharply. PCOS is managed with oral contraceptives, anti-androgen medications, and lifestyle changes. Virilization from a tumor requires imaging and surgery. Virilization from non-classic CAH requires cortisol-replacement strategy.
The overlap in symptoms means that clinicians seeing a woman with excess hair growth and irregular periods need to keep the rarer diagnoses in the back of their minds, even though PCOS will be the answer the vast majority of the time. The clinical guidance is fairly consistent: if symptoms are progressing rapidly, if testosterone levels are very high, or if the patient does not respond to standard PCOS treatment, further investigation is warranted to rule out tumors and adrenal enzyme deficiencies.24PubMed Central. Differentiating Polycystic Ovary Syndrome from Adrenal Disorders The threshold that raises the most concern is a total testosterone level above roughly three times the upper normal limit, a level that is uncommon in PCOS but characteristic of androgen-secreting tumors.25PubMed Central. Total testosterone levels are often more than three times elevated in patients with androgen-secreting tumours
Accidental Exposure in Children
Secondary testosterone transfer to children is a problem that keeps showing up in case reports and remains poorly recognized by many families. The scenario is straightforward: a father or household member applies testosterone gel to the skin (typically the shoulders, arms, or abdomen), and a child is exposed through cuddling, shared bedding, or contact with unwashed hands. Children are far more sensitive to exogenous androgens than adults, and even small amounts transferred through skin contact can trigger precocious pubic hair growth, genital enlargement, accelerated bone maturation, and behavioral changes.26PubMed. Virilization in two pre-pubertal children exposed to topical androgen
The good news is that in most reported cases, once the exposure is identified and stopped, the virilization largely resolves in children, whose tissues have not yet undergone the permanent structural changes that come with prolonged androgen exposure in adults. But the window for reversal is not unlimited. If the exposure goes unrecognized for months, bone age can advance significantly, which may ultimately reduce final adult height. Any unexplained signs of early puberty in a young child should prompt questions about potential androgen sources in the household, including topical products used by any family member.