Polycystic ovary syndrome (PCOS) is the most common hormonal disorder in women of reproductive age, affecting approximately 8-13% globally according to the World Health Organization. It is defined clinically using the Rotterdam criteria: a woman meets the diagnosis if she has at least two of three features, irregular ovulation, elevated androgens (clinical or biochemical), and polycystic-appearing ovaries on ultrasound. Despite the name, ovarian cysts are not required for the diagnosis, and their presence alone does not establish it.

The hormonal picture in PCOS is complex and varies between individuals. Understanding the core mechanisms, insulin resistance driving androgen excess, and LH hypersecretion disrupting ovulation, clarifies why different women respond to different treatments.

The Insulin-Androgen Connection

Insulin resistance is present in approximately 50-80% of women with PCOS, including many who are not overweight. In PCOS, insulin resistance in peripheral tissues (muscle, fat) is accompanied by preserved insulin sensitivity in the ovaries. When the pancreas compensates for peripheral resistance by producing more insulin, the ovaries remain responsive and convert that excess insulin signaling into increased androgen production, primarily testosterone and androstenedione.

These elevated androgens act on the hypothalamus to disrupt GnRH pulsatility, which alters the LH-to-FSH ratio. In PCOS, LH secretion is elevated relative to FSH, which further stimulates androgen production in the ovarian theca cells and impairs follicle maturation. Follicles fail to complete development, accumulate in the ovary (producing the “polycystic” appearance), and the cycle repeats.

This insulin-androgen-LH cycle is self-reinforcing and explains why weight loss, by reducing insulin resistance, often improves all three PCOS features simultaneously.

Androgen Excess: What It Produces Clinically

The clinical manifestations of androgen excess in PCOS include:

Hirsutism: Excess hair growth in androgen-sensitive areas, face, chest, abdomen, and inner thighs. Assessed using the Ferriman-Gallwey score. Present in approximately 70% of women with PCOS.

Acne: Often severe and affecting the jaw and lower face, a pattern driven by androgen stimulation of sebaceous glands. Adult acne in women without a clear cause warrants PCOS evaluation.

Androgenic alopecia (female pattern hair loss): Thinning at the crown and top of the scalp, similar to the pattern in men. Women who develop hair loss without a thyroid or iron deficiency explanation should be tested for PCOS and elevated androgens. The full range of causes of female hair loss is covered in Why Women Lose Hair: The 6 Most Common Causes and What Helps.

Diagnosing PCOS: Which Labs Matter

A diagnosis of PCOS requires ruling out other causes of androgen excess and irregular cycles before confirming the diagnosis by exclusion and Rotterdam criteria.

Essential labs:

  • Total testosterone (elevated in approximately 60% of PCOS cases)
  • Free testosterone or SHBG (more sensitive for borderline elevations)
  • DHEA-S (elevated DHEA-S suggests adrenal androgen contribution; very high levels warrant evaluation for adrenal tumors)
  • LH and FSH (LH:FSH ratio above 2:1 supports PCOS but is not required for diagnosis)
  • 17-hydroxyprogesterone (rules out congenital adrenal hyperplasia, a mimic of PCOS)
  • TSH (thyroid dysfunction can cause cycle irregularity and should be excluded)
  • Prolactin (elevated prolactin causes irregular cycles and should be excluded)
  • Fasting glucose and insulin, hemoglobin A1c (assess insulin resistance and diabetes risk)

Treatment Options With Evidence

Lifestyle modification: Weight loss of 5-10% in overweight women with PCOS consistently improves insulin sensitivity, reduces androgens, and restores ovulation in many cases. This is not a minimal intervention, it is the most evidence-supported first-line treatment for PCOS in overweight patients and often more effective than medication alone.

Combined oral contraceptives (COCs): First-line pharmacological treatment for managing menstrual irregularity and androgen-mediated symptoms (hirsutism, acne). They work by suppressing LH and thus androgen production, and by increasing SHBG, which reduces free testosterone. They do not address insulin resistance.

Metformin: An insulin sensitizer that reduces hepatic glucose production and improves peripheral insulin sensitivity. In PCOS, metformin reduces insulin levels, which secondarily reduces ovarian androgen production. It is FDA-approved for type 2 diabetes and commonly prescribed off-label for PCOS. Meta-analyses show it improves menstrual regularity and reduces androgen levels, though less effectively than COCs for symptom control.

Spironolactone: An androgen receptor blocker that reduces hirsutism and acne. Not appropriate during pregnancy or for women trying to conceive. Typically used in combination with COCs.

GLP-1 medications: Emerging evidence supports GLP-1 receptor agonists in PCOS management, particularly in overweight women. By improving insulin sensitivity and producing weight loss, they address the root insulin-androgen axis. This is an active research area without long-term PCOS-specific approval, but clinical use is increasing.

Clomiphene or letrozole: Used specifically for ovulation induction in women with PCOS who want to conceive. Letrozole has largely replaced clomiphene as first-line for fertility treatment in PCOS based on better live birth rates in the PPCCOS trial.