NICE vs SIGN: Management of Polycystic Ovary Syndrome (2025) - A Clinical Comparison
Polycystic Ovary Syndrome (PCOS) is a common endocrine disorder affecting individuals of reproductive age. In the UK, clinicians primarily rely on two national evidence-based guidelines: the National Institute for Health and Care Excellence (NICE) guideline and the Scottish Intercollegiate Guidelines Network (SIGN) guideline. While both aim to standardise and improve care, there are important distinctions in their approach. This comparison focuses on the 2023 NICE guideline (NG200, updated 2025) and the 2024 SIGN guideline (SIGN 176), highlighting key differences and practical implications for UK clinical practice.
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Diagnosis and Assessment
The diagnostic criteria form the most significant divergence between the two guidelines, influencing initial assessment and identification of patients.
NICE (NG200)
- Diagnostic Criteria: Recommends using the Rotterdam criteria. A diagnosis requires the presence of at least two of the following three features:
- Ovulatory dysfunction (oligo- or anovulation).
- Clinical and/or biochemical hyperandrogenism.
- Polycystic ovaries on ultrasound.
- Key Emphasis: Strong focus on patient-centred care from the outset. Stresses the importance of a positive, timely diagnosis, comprehensive information provision, and addressing emotional and psychological well-being at the first consultation.
- Ultrasound: Specifies that an ultrasound is not required for diagnosis if the other two Rotterdam criteria are met. A transabdominal ultrasound can be considered if a transvaginal scan is unacceptable to the person.
SIGN (SIGN 176)
- Diagnostic Criteria: Also uses the Rotterdam criteria, aligning with NICE.
- Key Emphasis: Provides more detailed, technical guidance on the assessment of each criterion:
- Biochemical Hyperandrogenism: Recommends measuring calculated free testosterone or free androgen index (FAI) as the first-line test. Provides specific cut-off values for elevated testosterone relative to local laboratory reference ranges.
- Ultrasound: Offers more specific technical details on performing the ovarian ultrasound, including follicle number per ovary and ovarian volume thresholds, adhering to the international consensus.
Practical Takeaway: Both guidelines use Rotterdam criteria, ensuring diagnostic consistency across the UK. NICE places greater emphasis on the patient experience at diagnosis, while SIGN provides more granular, technical detail on biochemical and ultrasound assessment, which can be particularly useful for specialists or in complex cases.
First-Line Treatment and Lifestyle Management
Both guidelines concur that lifestyle intervention (diet and exercise) is the cornerstone of management for overweight and obese individuals with PCOS. However, their recommendations on pharmacological first-line therapy differ.
NICE (NG200)
- First-Line for Menstrual Irregularity/Hirsutism: Recommends metformin as a first-line pharmacological treatment option alongside lifestyle advice for managing metabolic and menstrual symptoms, particularly for those with a BMI over 25.
- Contraception: Offers a broader range of first-line options. If contraception is desired, the combined oral contraceptive pill (COCP) is recommended. If not, metformin or a progesterone-only pill (e.g., cyclical micronised progesterone or dydrogesterone) is suggested for menstrual regulation.
SIGN (SIGN 176)
- First-Line for Menstrual Irregularity/Hirsutism: Recommends the combined oral contraceptive pill (COCP) as the first-line pharmacological treatment for menstrual regulation and hirsutism.
- Metformin: Positions metformin primarily for women with impaired glucose tolerance or type 2 diabetes, or for those struggling to conceive (in conjunction with fertility treatments). It is not promoted as a first-line general symptom management drug.
Practical Takeaway: This is a major difference. For a patient with a BMI of 30 seeking menstrual regulation but not contraception, a clinician following NICE might initiate metformin, while a clinician following SIGN would be more likely to recommend a cyclical progesterone or, if ineffective, consider the COCP. This decision point requires a detailed discussion of the patient's preferences, metabolic profile, and contraceptive needs.
Management of Infertility
The guidelines are largely aligned on the stepped approach to fertility management.
- Shared Recommendations: Both advise weight loss for overweight women as a first step. Letrozole is recommended as the first-line pharmacological ovulation induction agent, a shift from the historical use of clomiphene citrate.
- Metformin in Fertility: NICE suggests considering metformin alongside lifestyle changes for women trying to conceive, especially if they have a high BMI. SIGN recommends metformin in addition to lifestyle changes for women with a BMI >25 to improve ovulation and metabolic health before or during fertility treatment.
- In Vitro Fertilisation (IVF): Both guidelines recommend IVF as a third-line option if ovulation induction with letrozole (and sometimes gonadotrophins) fails.
Practical Takeaway: The management of infertility is well-harmonised, with letrozole established as the primary ovulation induction drug. The use of metformin as an adjunct in overweight women is supported by both, though NICE gives it a broader role.
Special Situations: Adolescents and Peri/Menopause
Adolescents
- NICE: Provides detailed guidance on diagnosing PCOS in adolescents, cautioning that ultrasound is not recommended due to the high prevalence of multi-follicular ovaries in this age group. Diagnosis should be based on irregular menstrual cycles and hyperandrogenism persisting for 2+ years post-menarche.
- SIGN: Also advises caution and recommends against using ultrasound for diagnosis in adolescents. The focus is on lifestyle management, with COCP considered if pharmacological treatment for menstrual dysfunction is required.
Peri/Menopause
- Both guidelines acknowledge the lack of evidence in this population. The focus shifts to managing long-term metabolic risks (cardiovascular disease, type 2 diabetes) and symptoms of androgen excess. Hormone Replacement Therapy (HRT) can be used for menopausal symptoms, as per general population guidance.
Practical Clinical Flow: A Synthesis
A pragmatic UK approach, synthesising both guidelines, might look like this:
- Assessment: Suspect PCOS based on symptoms (irregular periods, hirsutism, acne). Use Rotterdam criteria for diagnosis. For adolescents, rely on clinical and biochemical criteria only.
- Lifestyle Foundation: For all overweight/obese patients, offer structured lifestyle intervention (diet and exercise) as the first step.
- First-Line Pharmacological Choice:
- If contraception is desired → Offer COCP (aligned with both).
- If contraception is not desired → Discuss options: NICE supports metformin or cyclical progesterone; SIGN favours cyclical progesterone, then COCP. Base the choice on patient preference, metabolic parameters (e.g., insulin resistance), and side effect profiles.
- Infertility: Offer letrozole for ovulation induction. Consider adjunctive metformin if BMI >25.
- Long-Term Monitoring: Regularly assess BMI, blood pressure, and lipid profile. Offer an oral glucose tolerance test (OGTT) or HbA1c every 1-3 years, especially if additional risk factors exist.
Frequently Asked Questions (FAQs)
1. Which guideline should I follow in England? In Scotland?
NICE guidelines are the standard for England and Wales. SIGN guidelines are developed for, and are the standard in, Scotland. However, clinicians across the UK can benefit from consulting both to understand the evidence and different clinical reasoning.
2. What is the key practical difference in daily practice?
The most noticeable difference is the first-line pharmacological management for menstrual symptoms in the absence of a need for contraception. NICE's inclusion of metformin offers an alternative for patients who cannot or do not wish to take the COCP, focusing on the underlying insulin resistance.
3. Are the guidelines conflicting on diagnosis?
No. Both use the Rotterdam criteria, ensuring diagnostic consistency. The difference lies in the depth of technical detail provided by SIGN versus the stronger patient-communication focus in NICE.
4. How do they differ in managing hirsutism?
Both recommend cosmetic measures and COCP as first-line. NICE also includes metformin as an option. Both agree that anti-androgens (e.g., spironolactone, finasteride) are second-line treatments and require reliable contraception due to teratogenic risks.
5. What about the new GLP-1 receptor agonists?
As of 2025, neither guideline has incorporated GLP-1 receptor agonists (e.g., semaglutide) into their formal recommendations for PCOS management. Their use remains within specialist weight management services or clinical trials, not for routine PCOS care.
Source Links
- NICE Guideline NG200 (2023, updated 2025): Polycystic ovary syndrome: assessment and management
- SIGN Guideline 176 (2024): Polycystic Ovary Syndrome