Phylactou M, Clarke SA, Patel B, et al. - Researchers conducted the study for reviewing clinical, biochemical and radiological parameters that could help the clinician in differentiating polycystic ovary syndrome (PCOS) and functional hypothalamic amenorrhoea (FHA) as a cause of menstrual disturbance. According to results, FHA is uncommon in women with BMI > 24 kg/m², while both PCOS and FHA can occur in women with lower BMIs. The levels of AMH in PCOS are markedly elevated, but milder rises in FHA can also be observed. Similarly, polycystic ovarian morphology is more frequently seen in FHA than in healthy women. LH, androgen, insulin, AMH and SHBG levels, endometrial thickness and cortisol response to CRH are characteristics that are differentially altered between PCOS and FHA. Other promising diagnostic tests with the potential to differentiate these two conditions pending further study involve assessment of 5‐alpha‐reductase activity, leptin, INSL3, kisspeptin and inhibin B levels. Further data directly comparing the discriminatory potential of these markers to distinguish PCOS and FHA in women with secondary amenorrhoea would be of value in defining the objective likelihood of PCOS or FHA diagnosis.