The purpose of this study is to examine whether a larger dosage of estrogen than the one used today will secure the development of a normal sized uterus and increase the strength of the bones in girls and young women with Turner syndrome.

The purpose is also to evaluate whether aortic dilatation is present in this group of patients, and if the estrogen dosage will influence the emotional well-being and self-esteem of the patients.

Turner syndrome is a common chromosomal disorder with only one X-chromosome or partial deletions in one X-chromosome in all or some of the cell-lines in the body. Appr. 18 girls/year are being born with the syndrome in Denmark. The syndrome is mostly known for reduced final height and the lack of pubertal development with infertility, but it is also known for diseases influencing other parts of the body like the heart with the risk of development of aortic dilatation and subsequently dissection with the risk of rupture, profuse bleeding and sudden death. Reduced bone strength and increased risk of bone fracture are also features of the syndrome. Treatment with growth hormone and female sex-hormones are well-established treatments.

Girls and young women with Turner syndrome ages 10 to 21 years will participate. The girls ages 15 to 21 years will randomly and double blindly receive treatment with either 2 mg or 4 mg estrogen for 5 years. Yearly examinations with blood tests, physical examinations, questionnaires, ultrasound and MR-scan of the internal female genitalia, DEXA-scan of the bones and MR-scan of the heart will be performed.

Inclusion Criteria:

• Verified Turner syndrome
• Ages 10-25 years

Exclusion Criteria:

• Contraindications to the MR-scan
• Contraindications to the trial medication
• Severe or chronic sickness with impact on the parameters of the study or incompatibility with the trial medication
• Intake of medications with interactions with trial medication