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Answerback: Is USS always needed in PCOS diagnosis?

Our experts answer your clinical questions

Our experts answer your clinical questions

If someone has a clear clinical presentation of polycystic ovary syndrome (PCOS), does an ultraound scan (USS) add anything useful? For a diagnosis of PCOS, two out of the following three criteria should be met (European Society of Human Reproduction and Embryology/American Society for Reproductive Medicine consensus statement, 2003):

  • Oligo-amenorrhoea
  • Clinical or biochemical hirsutism
  • Ultrasound evidence of ovaries of polycystic morphology.

However, other causes of oligo-amenorrhoea and hirsutism must first be excluded. Causes of oligo-amenorrhoea include premature ovarian failure and hypothalamic-pituitary-ovarian axis disorders. Your patient should have her serum levels of follicle-stimulating hormone (FSH), luteinising hormone (LH), prolactin, and thyroid-stimulating hormone (TSH) measured.

High levels of FSH indicate ovarian failure. FSH is normal in PCOS. Very low FSH and LH levels may suggest a hypothalamic problem secondary to low body weight or tumour. A normal FSH but raised LH (LH/FSH ratio >2) suggests PCOS but is not one of the diagnostic criteria.Causes of hirsutism include late-onset congenital adrenal hyperplasia (CAH), Cushing's syndrome, or an androgen-secreting tumour.

Serum testosterone should be measured (normal <3nmol/litre). Levels above 5nmol/litre may still be due to PCOS but a different source of androgens must be considered. Late-onset CAH may be excluded with a serum 17-OH progesterone level. Measuring sex hormone-binding globulin (generally low in PCOS), free testosterone, androstenedione, and dehydroepiandrosterone sulphate may also help.

If these other diagnoses have been excluded then a USS is not strictly required. But as PCOS is a syndrome, the more factors that are present the stronger the diagnosis. So a scan, if available and acceptable to the patient, is still worth performing.

Tim Child, senior fellow in the University of Oxford and honorary consultant gynaecologist and subspecialist in reproductive medicine at the John Radcliffe Hospital in Oxford. Competing interests: none declared

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