Description
Polycystic ovarian syndrome (PCOS) is a common endocrine disorder affecting women of reproductive age, characterised by chronic anovulation, hyperandrogenism, and polycystic ovaries. It is one of the leading causes of female infertility.
Pathogenesis
The exact pathogenesis of PCOS is complex and not completely understood. However, it is believed to involve multiple factors including genetic predisposition, insulin resistance, increased luteinizing hormone (LH) secretion, and elevated androgen levels. The insulin resistance leads to compensatory hyperinsulinemia which stimulates the ovarian theca cells to produce excessive androgens.
Epidemiology, Risk Factors & Associations
- Approximately 5-20% of women of reproductive age are affected (varies depending on diagnostic criteria used)
- The primary risk factor for PCOS is obesity, occurring in 50-80% of patients.
- Other risks include family history, premature adrenarche, and low birth weight.
- Common associations are metabolic syndrome, type 2 diabetes, cardiovascular disease, and endometrial cancer as well as endometrial hyperplasia (pre-cancerous condition)1.
Clinical Features
The classic triad:
- Present with menstrual irregularities – oligomenorrhoea and/or amenorrhoea
- Signs of hyperandrogenism (such as hirsutism, acne, and alopecia)
- Obesity
Complications
- Sub- or infertility due to chronic anovulation
- Increased risk of gestational diabetes and pre-eclampsia
- Metabolic syndrome and cardiovascular disease
- Increased risk of endometrial hyperplasia and cancer due to unopposed oestrogen
- Increased risk of ovarian hyperstimulation syndrome when undergoing IVF
Pathological Features
Histopathology
- Macroscopic: Enlarged ovaries with smooth, pearl-white outer surface.
- Microscopic: Numerous small follicles in various stages of atresia, thickened ovarian stroma.
Serology
- Elevated levels of serum androgens (testosterone, androstenedione)
- Elevated LH with normal or low follicle-stimulating hormone (FSH) levels (LH:FSH ratio > 2:1)
Biochemistry
- Often associated with insulin resistance and hyperinsulinemia
Radiological Features
General Features
- Characteristically demonstrates enlarged ovaries with numerous small peripheral cysts (typically >10 in each ovary, 2-9mm in diameter) giving a string of pearls appearance.
- Enlarged ovaries
- The ovarian stroma is often hyperechoic on ultrasound.
- Associations: endometrial hyperplasia
MRI
- T1WI: Ovaries are usually normal in signal intensity. Follicles are uniformy low in signal. Central stroma is intermediate signal with respect to normal myometrium.
- T2WI: Multiple small follicles may be seen as high-signal-intensity lesions on the periphery of the ovaries. Central stroma is low signal.
- T1 C+: No specific enhancement pattern for PCOS
- DWI/ADC: Not typically used in the evaluation of PCOS
Ultrasound
- Transvaginal ultrasound is the imaging modality of choice.
- Shows enlarged ovaries with multiple small peripheral cysts (string of pearls sign) measuring 2 – 9 mm
- Hyperechoic central stroma may be seen
- Associated endometrial hyperplasia (premenopausal normal thickness < 8 mm, however 15 mm is considered the upper limit of normal in the secretory phase)
Grading and Staging
There is no widely accepted grading or staging system for PCOS.
Diagnosis
Diagnosis of PCOS is based on the Rotterdam criteria, requiring at least two of the following:
1. Clinical or biochemical signs of hyperandrogenism
2. Ovulatory dysfunction
3. Polycystic ovarian morphology on ultrasound.
- Imaging criteria (revised 2018 international consensus guidelines) for polcystic ovaries is based on the number of follicles and ovarian volume. In patients older than 8 years postmenarche, using a high-frequency endovaginal probe, either of the following findings are sufficient for diagnosis:
- One or both ovaries demonstrate ≥ 20 follicles (supersedes Rotterdam criteria of >12 follicles.)
- One or both ovaries with volume > 10 mL (ensuring no corpora lutea, cysts or dominant follicles are present)
Differential Diagnosis
- Ovarian Hyperstimulation Syndrome (OHSS): This is a complication of fertility treatments, causing rapid ovarian enlargement with numerous cysts, abdominal discomfort, and occasionally severe complications. Distinguished by its acute onset following hormonal stimulation for IVF. Imaging reveals markedly enlarged ovaries with multiple cysts, often associated with ascites and potentially pleural effusion.
- Ovarian Hyperthecosis: Similar to PCOS but presents in postmenopausal women. Enlarged ovaries lack multiple peripheral follicles.
- Congenital Adrenal Hyperplasia (CAH): Presents with hyperandrogenism and polycystic ovaries, but associated with elevated 17-hydroxyprogesterone levels.
- Cushing’s Syndrome: Presents with hyperandrogenism but also features of hypercortisolism and abnormal dexamethasone suppression test.
- Androgen-secreting tumours: Mimic PCOS with hyperandrogenism but have a rapid onset and significantly elevated androgen levels. Unilateral ovarian mass may be seen.
- Hypothyroidism: Can show menstrual irregularities and enlarged ovaries with multiple cysts. Other clinical features of hypothyroidism and abnormal thyroid function tests differentiate it from PCOS.
Management
Management of PCOS typically involves lifestyle modifications, such as diet and exercise for weight management. Medical treatments may include hormonal contraceptives, anti-androgens, and insulin-sensitising drugs. Infertility can be managed with ovulation induction agents, in vitro fertilisation, or surgery.
References