Polycystic Ovary Syndrome (PCOS)
NICE CKS Polycystic ovary syndrome. Last revised: Mar 2025.
NICE Clinical guideline [CG156] Fertility problems: assessment and treatment. Last updated: Sep 2017.
International evidence-based guideline for the assessment and management of polycystic ovary syndrome (PCOS) 2023.
The diagnosis and management sections have been restructured and refined to improve clarity and usability.
Date: 12/12/25
Background Information
Definition
PCOS is a heterogeneous endocrine disorder that appears to emerge at puberty, characterised by 1) hyperandrogenism, 2) ovulation disorder, and 3) polycystic ovarian morphology.
Aetiology and Pathophysiology
The exact cause is unknown, likely to be multifactorial (both genetic and environmental factors)
The primary driving event is peripheral insulin resistance and subsequent hyperinsulinaemia, which results in:
- Hyperandrogenism
- ↑ LH secretion and disrupted LH/FSH balance
Complications
Main complications:
- Pregnancy-related problems
- Infertility – PCOS is the single most common cause of infertility in young women
- Pregnancy complications (miscarriage, gestational diabetes, pregnancy-induced hypertension)
- Endometrial cancer (chronic anovulation → absence of progesterone production → unopposed oestrogen effect)
- CVD, metabolic syndrome, NAFLD
- Obstructive sleep apnoea
- Psychological disorders (mainly mood and anxiety disorders)
Diagnosis
Clinical Features
Key clinical features can be grouped as follows:
| Category | Features |
|---|---|
| Disrupted LF/FSH balance |
|
| Hyperandrogenism features |
NB that PCOS does NOT cause features of virilisation (e.g. deep voice, reduced breast size, increased muscle bulk, and clitoral hypertrophy) |
| Hyperinsulinaemia features |
|
Diagnostic Criteria
PCOS can be diagnosed if at least 2 out of 3 of the following are present (Rotterdam criteria):
| Category | Description |
|---|---|
| Ovulatory dysfunction | Manifested as oligomenorrhoea / amenorrhoea |
| Hyperandrogenism (clinical OR biochemical evidence is sufficient) | Clinical evidence:
|
Biochemical evidence:
Androstenedione and DHEAS should only be measured if total testosterone is NOT elevated (both would be ↑ in PCOS) Note that ↑ LH:FSH ratio is supportive of PCOS, but no longer recommended to guide diagnosis |
|
| Supportive ultrasound findings | ≥20 follicles in at least 1 ovary |
NICE CKS notes that in adolescent girls, BOTH irregular menstrual cycles and hyperandrogenism are required to diagnose PCOS.
PCOS is diagnosed using the Rotterdam criteria (2 out of 3).
If both ovulatory dysfunction and hyperandrogenism are present, the diagnosis can be made without pelvic ultrasound.
Excluding Differential Diagnoses
Perform ALL the following tests to exclude other causes of oligomenorrhoea and amenorrhoea in patients with suspected PCOS:
| Test | Purpose |
|---|---|
| LH and FSH | Exclude premature ovarian failure
↑ LH:FSH ratio is supportive of PCOS (but no longer recommended to guide diagnosis, but common in exams). However, note that isolated ↑ FSH suggests ovarian insufficiency |
| Prolactin | Hyperprolactinaemia can cause subfertility and menstrual disturbances |
| TSH | Hyperthyroidism and hypothyroidism can cause menstrual disturbances |
Non-PCOS causes of hyperandrogenism (such as late-onset congenital adrenal hyperplasia, Cushing’s syndrome, or androgen-secreting tumours) are more likely if any of the following features are present:
- Signs of virilisation (e.g. deep voice, reduced breast size, increased muscle bulk, and clitoral hypertrophy)
- Rapidly progressing hirsutism (<1 year between hirsutism being noticed and seeking medical advice)
- Significantly elevated total testosterone level (>5 nmol/L or >2x the upper limit of normal)
Management
Approach:
- All patients → cardiovascular and metabolic risk management
- If patient is NOT trying to conceive → focus on symptom management
- If patient IS trying to conceive → focus on infertility management
Cardiovascular and Metabolic Risk Management
| Aspect | Tests / management |
|---|---|
| Encourage a healthy lifestyle |
|
| Optimise weight management |
|
| Smoking cessation |
|
| Metformin | Metformin has been used off-label to treat PCOS
Metformin is safe in those who are trying to conceive |
| Blood pressure |
|
| Glycaemic status |
|
| Lipid status |
|
Endometrial protection:
If there is prolonged amenorrhoea (<1 period every 3 months) or abnormal vaginal bleeding → give cyclical progesterone to induce a withdrawal bleed, then refer for TVUS to assess endometrial thickness
- If endometrial thickness >10mm / unusual appearance → endometrial sampling
- If normal endometrium → offer treatment to prevent endometrial hyperplasia
- Cyclical progestogen (e.g. medroxyprogesterone)
- Low-dose COCP
- LNG-IUD
PCOS Symptoms Management
COCP is considered the 1st line pharmacological treatment for PCOS symptom control in patients NOT trying to conceive. It uniquely provides all the following benefits:
- Treats hyperandrogenism (↓ ovarian androgen production, ↑ SHBG)
- Regulates menstrual cycles
- Provides endometrial protection
- Provides effective contraception
Key management aspects of PCOS symptoms:
| Weight loss (if the patient is overweight / obese) | Weight loss has immense benefits in PCOS, explain that it may:
|
| COCP | COCP should be offered to ALL patients, provided that:
|
| Treatment of specific hyperandrogenism features |
|
| Anti-androgens | Anti-androgens are NOT routine 1st line therapy, they should only be used if COCP and cosmetic / hair reduction therapies are not appropriate / ineffective
Options include:
|
Remember, if the patient is trying to conceive → most treatment options outlined here are inappropriate:
- COCP → contraindicated
- Anti-androgens → contraindicated
- Acne management → retinoids are contraindicated (both topical and oral), antibiotics apart from erythromycin are contraindicated (see the Acne Vulgaris article for more information)
Ones that are appropriate, even if trying to conceive:
- Weight loss → very important and beneficial
- Hair reduction and removal (e.g. shaving and waxing)
Infertility Management
Infertility management is only indicated for patients actively trying to conceive, as it 1) induces ovulation and 2) increases chance of pregnancy
It should NOT be offered to those who are not, as it provides no benefit outside fertility treatment.
If BMI ≥30:
- 1st line: attempt to lose weight (weight loss alone may already restore ovulation)
- Weight loss also improves response to ovulation induction agents and have +ve impact on pregnancy outcomes
If BMI <30 or weight loss did not work → offer ovulation induction
- 1st line: clomiphene citrate and/or metformin
- 2nd line:
- Clomiphene citrate + metformin (if not already offered), or
- Gonadotropins, or
- Laparoscopic ovarian drilling
For those who take clomiphene citrate:
- Offer ultrasound monitoring during at least 1st cycle of treatment to ensure the lowest effective dose (due to risk of multiple pregnancy and ovarian hyperstimulation syndrome)
- Do not continue treatment for >6 months
Letrozole in PCOS:
- Letrozole is an aromatase inhibitor
- Its use as ovulation induction in PCOS is off-label, and are NOT mentioned in NICE guidelines
- However, the International evidence-based guideline for the assessment and management of polycystic ovary syndrome 2023 recommends that “Letrozole should be the first-line pharmacological treatment for ovulation induction in infertile anovulatory women with PCOS, with no other infertility factors“
References