Introduction Functional hypothalamic amenorrhoea (FHA) is a condition characterised by the absence of menses due to suppression of the hypothalamic-pituitary-ovarian axis.

Objective The purpose of the study was to estimate uterine and ovarian sizes in adolescents with FHA and to compare these results with findings in peers having regular menstrual cycles.

Design Prospective case-controlled study.

Settings Vilnius University Hospital Santariskiu Klinikos, Lithuania.

Patients Lithuanian adolescents—45 with FHA and 40 comparison group participants.

Main outcome measures We assessed ultrasound measurements of internal reproductive organs, levels of luteinising hormone, follicle-stimulating hormone, prolactin, oestradiol and calculated body mass index (BMI).

Results The mean age of the participants was 16.3±1.2 years, the mean age after menarche—3.6 years. In adolescents with FHA the BMI was 17.8±1.8 kg/m² and 20.4±1.4 kg/m² in the comparison group, p<0.001. The uterine volume (14.7±6.3 cm³ vs 31.7±10.6 cm³, p<0.001), cervical length (2.3±0.4 cm vs 2.6±0.5 cm, p=0.03), volume of both ovaries (9.3±3.6 cm³ vs 13.8±4.3 cm³, p<0.001) and levels of LH (2.70±2.59 vs 6.01±2.44, p<0.001) were significantly lower in girls with FHA. A significantly positive correlation between volume of uterus and levels of LH (r=0.415; p<0.001) was found. We identified a positive correlation between uterine volume, uterine corpus length, cervical length, ovarian volume and weight, BMI.

Conclusions In adolescents with FHA the dimensions of uterus and ovaries were smaller than in girls having regular menstrual cycles. Our study confirmed the influence of oestrogen on uterus size: oestrogen deficiency causes a reduction in uterine size. Uterine size and ovarian size correlate positively with BMI.