Why Does PCOS Cause High Testosterone?

Polycystic ovary syndrome drives testosterone up through several reinforcing biological loops rather than a single broken switch. The ovaries overproduce androgens because they receive too-strong signals from the brain and too much stimulation from insulin, while the body’s normal checks on androgen levels falter at the same time. Understanding which loops are loudest in a given person helps explain why PCOS looks so different from one woman to the next and why treatments target such different parts of the system.

The Brain Signal That Tips the Balance

One of the earliest disruptions in PCOS happens in the hypothalamus, the part of the brain that controls reproductive hormones. The hypothalamus releases gonadotropin-releasing hormone (GnRH) in rhythmic pulses, and those pulses tell the pituitary gland how much luteinizing hormone (LH) and follicle-stimulating hormone (FSH) to secrete. In women with PCOS, GnRH fires roughly 40% faster than normal, shifting from about one pulse every 90 minutes to one pulse every 60 minutes.¹ That faster tempo favors LH production over FSH production, so LH levels climb while FSH stays relatively flat or low.

LH is the main hormonal signal telling ovarian theca cells to make androgens. When the pituitary pours out extra LH, the theca cells respond by cranking up androgen synthesis. This alone would raise testosterone, but the problem is compounded by the fact that FSH, the hormone that normally helps convert androgens into estrogen inside neighboring granulosa cells, is not keeping pace. The result is a lopsided hormonal environment where the raw material for testosterone keeps being made but is not efficiently converted downstream.

How Insulin Pours Fuel on the Fire

Insulin resistance is present in a large share of women with PCOS, and it does not just raise blood sugar. Insulin acts directly on ovarian cells, stimulating androgen production and working synergistically with LH to amplify the signal that theca cells already receive.² In other words, even if LH were only mildly elevated, high circulating insulin can magnify its androgen-boosting effect, which helps explain why symptoms of excess androgens tend to be more pronounced in women who also carry extra weight or have significant insulin resistance.

Insulin also lowers the liver’s production of sex hormone-binding globulin (SHBG), a protein that acts like a sponge for testosterone in the bloodstream. Bound testosterone is biologically inactive; it cannot enter tissues and trigger effects like acne, oily skin, or hair growth. When insulin pushes SHBG down, a larger fraction of total testosterone becomes “free” and active. Research across multiple PCOS subtypes has confirmed a significant inverse relationship between insulin and SHBG levels.³ So insulin hits twice: it raises how much testosterone the ovaries make, and it increases how much of that testosterone is biologically active.

Overactive Enzymes Inside the Ovary

Even at the cellular level, PCOS theca cells appear to be wired differently. The key enzyme in androgen production is called CYP17A1, which catalyzes the chemical reactions that ultimately produce testosterone and its precursors. In PCOS theca cells, the gene encoding this enzyme is expressed at higher levels than in normal theca cells. Researchers have linked this to changes in a regulatory gene called ZNF217: when ZNF217 expression drops, as it does in PCOS theca cells, CYP17A1 expression rises, leading to more androgen output.⁴ This means PCOS ovaries are not just getting stronger signals from LH and insulin. The machinery inside the cells is also set to produce more androgens per unit of signal.

Another piece of the ovarian puzzle involves anti-Müllerian hormone (AMH), which is produced by the small, growing follicles that accumulate in polycystic ovaries. AMH levels are typically elevated in PCOS, and AMH blocks aromatase, the enzyme that converts androgens into estrogen inside granulosa cells.⁵ This has been confirmed in human granulosa cell cultures, where AMH suppresses the gene responsible for aromatase activity.⁶ So the androgens that theca cells make are not being efficiently cleared through their normal exit route of conversion to estrogen. They build up instead.

The Adrenal Gland’s Separate Contribution

The ovaries get most of the attention, but roughly 20 to 30% of women with PCOS also overproduce androgens from their adrenal glands.⁷ These women show elevated levels of DHEA and DHEAS, adrenal precursor hormones that can be converted into testosterone in peripheral tissues. The adrenal overproduction does not seem to come from a defect in the brain’s control of the adrenal axis. Instead, the adrenal cortex itself appears to have an exaggerated steroidogenic response when stimulated by ACTH, the normal pituitary hormone that tells adrenal glands to work.⁸

Whether this exaggerated response comes from a larger adrenal gland, differences in enzyme activity, or some other structural change is still debated. Some evidence suggests the adrenal androgen excess is linked to insulin sensitivity as well as decreased activity of a specific steroidogenic enzyme (3-beta-hydroxysteroid dehydrogenase), particularly in women who still have regular cycles.⁹ This matters because it means some women with PCOS are getting a double dose of androgens, from the ovaries and the adrenals, through partially independent mechanisms.

How Body Fat and Inflammation Amplify Androgens

Body fat is not just a passive storage depot. Adipose tissue is metabolically active, and in PCOS it tends to be dysfunctional in ways that go beyond simply having too much of it. Research suggests that adipose tissue dysfunction, more than the total amount of body fat, drives the metabolic and inflammatory abnormalities seen in PCOS.¹⁰ When fat cells enlarge (hypertrophy), they compress their own blood supply, creating localized oxygen deprivation that triggers an inflammatory cascade. Combined with androgen excess, this leads to chronic low-grade inflammation and the release of inflammatory signaling molecules like TNF and IL-6, which can feed back into both insulin resistance and altered sex steroid secretion.¹¹

Body fat also influences how androgens are processed at the tissue level. Women with PCOS show higher activity of an enzyme called 5-alpha-reductase, which converts testosterone into dihydrotestosterone (DHT), a more potent androgen. A meta-analysis confirmed that this increased enzyme activity is present in PCOS and is significantly associated with insulin resistance regardless of whether a woman is obese.¹² Even more striking, elevated 5-alpha-reductase activity has been detected in young daughters of women with PCOS during early childhood, suggesting this enzymatic difference may be present long before the syndrome becomes clinically apparent.¹³

Lean PCOS and Why Weight Is Not the Whole Story

A common misconception is that PCOS is an obesity-related condition. Many women with PCOS are lean, and they still have elevated testosterone. The mechanisms in lean PCOS lean more heavily on the neuroendocrine disruption (the fast GnRH pulses and high LH) and intrinsic ovarian enzyme overactivity, rather than on insulin-driven amplification. Studies comparing lean and obese women across different PCOS phenotypes have found that testosterone levels and the LH-to-FSH ratio are driven primarily by the type of PCOS (specifically whether there is both hyperandrogenism and ovulatory dysfunction) rather than by body weight alone.¹⁴

That said, obesity changes the clinical picture in specific ways. In a study of 263 women with PCOS, obese and lean women had similar total testosterone and androstenedione concentrations. But obese women had significantly lower SHBG, which meant their free (bioactive) testosterone was higher. They also showed greater 5-alpha-reductase activity and a higher prevalence of hirsutism (73% vs. 56%).¹⁵ So while the ovaries may produce roughly the same amount of testosterone in lean and obese PCOS, excess body fat changes how that testosterone is carried, converted, and experienced. The visible symptoms of androgen excess are often worse with more body fat, even if the total production is similar.

Genetics, Fetal Programming, and the Self-Perpetuating Cycle

PCOS runs in families, and the search for specific causal genes has been frustratingly slow. No single gene appears to cause the syndrome. Instead, common genetic variants that influence androgen activity and availability are associated with PCOS, and these variants may set the stage for a kind of prenatal programming.¹⁶ The hypothesis, well supported by animal models, is that a female fetus exposed to higher-than-normal androgens in the womb has her developing ovaries, brain, and metabolic tissues shaped in ways that predispose her to PCOS decades later. Research has specifically investigated how excess prenatal androgens alter gene expression and mitochondrial function in neonatal ovarian tissue.¹⁷

This creates a potential intergenerational feedback loop. A mother with PCOS and elevated androgens exposes her developing daughter to those androgens in the womb. The daughter’s tissues are programmed toward a PCOS phenotype. When she reaches puberty, her ovaries are already primed to overproduce androgens, and the cycle is set to repeat. It is not strictly genetic inheritance in the traditional sense; it involves epigenetic changes, where gene expression is altered without the DNA sequence itself changing.

Environmental Chemicals That May Push the System Further

Bisphenol A (BPA), a chemical found in many plastics and food packaging, has come under scrutiny as a possible contributor to PCOS. BPA mimics estrogen but also appears to disrupt androgen production directly. In laboratory studies, bisphenol compounds have been shown to stimulate ovarian cells to produce more androgens by dysregulating 17-alpha-hydroxylase, one of the same key enzymes already overactive in PCOS theca cells.¹⁸ Population studies have found that serum BPA levels are positively correlated with testosterone and with markers of metabolic dysfunction in women with PCOS.¹⁹ BPA’s ability to bioaccumulate with daily exposure and activate non-genomic signaling pathways may alter both metabolic and reproductive function, promoting hyperandrogenism, insulin resistance, and chronic inflammation.²⁰

Whether BPA actually causes PCOS or merely worsens it in genetically predisposed women is an open question. Correlation studies cannot prove causation, and human exposure to BPA is nearly universal, making it hard to separate its effect from background risk. But the biological plausibility is strong enough that it is receiving serious research attention.

The Gut Microbiome Connection

A growing body of work links the gut microbiome to PCOS, though the field is still young and much of the evidence comes from animal models. The basic idea is that gut bacteria influence insulin signaling and inflammation, both of which feed the androgen-producing loops described above. Research has shown that gut microbiota can regulate insulin synthesis and secretion and affect androgen metabolism and follicle development.²¹ In rat models, high-fat diets and androgen exposure both reshape gut microbial communities, and testosterone levels negatively correlate with microbial diversity.²² It is plausible that reduced microbial diversity worsens insulin resistance, which in turn worsens androgen production, creating yet another reinforcing loop. But translating rodent microbiome findings to human clinical recommendations is still premature.

What Treatments Target and Why

Because high testosterone in PCOS is not caused by a single defect, treatments tend to target different nodes of the system. Metformin, an insulin sensitizer, reduces androgen levels partly by lowering insulin’s stimulatory effect on the ovaries. Spironolactone blocks androgen receptors in tissues like hair follicles and skin, and also has some ability to improve metabolic parameters.²³ A network meta-analysis comparing multiple drug classes found that metformin, spironolactone, statins, and combinations of these agents all significantly reduced testosterone levels compared to placebo.²⁴ Combined oral contraceptives are another common intervention; by providing steady estrogen and progestin, they suppress the pituitary’s LH output and raise SHBG, attacking the problem from the brain end and the binding-protein end simultaneously.

The variety of effective drug targets reinforces the point that PCOS-related hyperandrogenism is not a single-pathway disease. A treatment that works well for one woman might do little for another whose androgen excess is driven by a different combination of mechanisms.

Long-Term Health and What Testosterone Levels Actually Predict

The metabolic consequences of PCOS extend well beyond reproductive health. The combination of insulin resistance, androgen excess, and chronic inflammation raises the risk of glucose intolerance, type 2 diabetes, fatty liver disease, abnormal cholesterol profiles, and high blood pressure over the long term.²⁵ It is tempting to assume that the women with the highest testosterone face the greatest long-term risk, but the picture is more nuanced than that. A 37-year prospective study found that while higher free testosterone in young women with PCOS was associated with more pronounced metabolic and hormonal profiles early on, it did not significantly predict long-term morbidity or mortality. Interestingly, women in the lower-testosterone group had higher rates of depression and hypothyroidism, while autoimmune diseases were more common in the higher-testosterone group.²⁶ These findings suggest that testosterone level alone is not the primary driver of long-term complications, and that broader metabolic factors matter more for prognosis.

An Evolutionary Puzzle

PCOS affects a large proportion of reproductive-age women worldwide and has a strong hereditary component. Given that it impairs fertility, its persistence at such high prevalence is an evolutionary puzzle.²⁷ One prominent hypothesis frames PCOS as the extreme end of a normally beneficial adaptation. In ancestral environments, relatively higher testosterone in women conferred advantages in strength, muscularity, and physical robustness. A series of systematic reviews found that this hypothesis is largely supported: testosterone levels in women are indeed associated with measures of athleticism and physical capacity.²⁸ Under this model, PCOS is not so much a disease that evolved as it is the far tail of a trait distribution that was, on average, beneficial. The genes that push testosterone modestly upward may have been positively selected; PCOS emerges when too many of those variants combine, or when modern environmental factors like caloric excess and sedentary lifestyles push a genetically loaded system past its tipping point.

This framing does not make PCOS any less real or disruptive for the women who have it. But it does help explain why the genetic architecture behind it has not been pruned away by natural selection and why the condition is so common in the first place.