• Amenorrhoea;
  • anorexia nervosa;
  • eating disorder;
  • menstruation

Aim: To investigate the weight requirements for return of menstruation in teenage girls with eating disorders (ED), weight loss and secondary amenorrhoea. Methods: Growth charts from the school health services and measurements of weight and stature at assessment and during follow-up were obtained for 127 girls with ED, secondary amenorrhoea and subsequent return of menstruation. Measurements were used to estimate weight and body mass index (BMI) before puberty, at menarche, at the highest weight prior to the onset of the ED, at the last menstruation preceding amenorrhoea, at the lowest weight during treatment, and at return of menstruation. Results: Before onset of the ED, the girls were taller, heavier and less lean than the population average as evidenced by standard deviation scores (SDS) for weight, height and BMI above zero. Weight loss started from an average weight of 58.9 ± 9.8 kg (mean ± SD), a last menstruation occurred at 51.5 ± 6.9 kg, the lowest weight during treatment was 45.6 ± 7.0 kg and menstruation returned at 52.9 ± 6.0 kg. Return of menstruation occurred within a wide weight range. However, if weight at return of menstruation was expressed in SDS, it could be predicted by a linear regression on weight SDS at loss of menstruation (r2= 0.76; p > 0.001).

Conclusions: The weight level required for return of menstruation is highly individual but can be predicted by the weight at which menstruations cease. In the treatment of ED, there is a need for such individual weight targets—a target based on the population weight for height and/or age may be too generalized and too low.