Introduction/Background Following its introduction in the 1960s, the use of Hormonal Replacement Therapy (HRT) to treat postmenopausal symptoms has increased from 30% to 50%. However, this has resulted in an increased utilisation of services for the investigation of women with increased endometrial thickness (ET) subsequent to HRT.

Methodology This was a retrospective case-control study carried out in a tertiary institute in the UK. Data of 452 women referred to the hysteroscopy clinic for postmenopausal bleeding was collected over a 2-year period. The women were divided into 2 cohorts – group 1 on HRT (N= 206) and group 2- not on HRT (N= 246).

Results The mean age and BMI was 57 years and 27.54 kg/m² in group 1 and 61.54 years and 29.51 kg/m² in group 2. Analysis of group 1 revealed that the mean ET was 9.5 mm (95% CI 6.152–12.85 mm) in women who were diagnosed with an endometrial malignancy (N=8) and 6.89 mm (95% CI 6.404–7.381 mm) in women with benign endometrial histology (N=148). This difference was statistically significant (t-test; p=0.0201). However, further evaluation using a ROC curve, an ET of 9.5 mm leads to a sensitivity of only 50% to cancer (specificity = 85.8%) while the current cut off, 4 mm, detected nearly all cancers. This result was further corroborated by a ROC analysis of the non-HRT group which demonstrated similar results.

Conclusion Increasing HRT utilisation will lead to a rise in the number of women with benign endometrial thickening. This may lead to a rise in unnecessary referrals. Our initial work has not demonstrated that increasing the ET cut off is useful in this group, however a downside of our work is the small number of patients with cancer in the HRT group. Thus larger robust studies would be useful to evaluate if this hypothesis has clinical merit.