Pre-pubertal Low Dose Transdermal Estradiol in Turner Syndrome

Inclusion Criteria: 1. Provision of signed and dated informed consent form 2. Stated willingness to comply with all study procedures and availability for the duration of the study 3. Female, aged 8 years up to 11 y and 180 days with karyotype confirmed Turner syndrome 4. FSH result\> 10miu/mL in the past 12 months. Since variability in FSH is not uncommon, a single measure of FSH \>10mIU/mL in the past calendar year will be deemed sufficient for inclusion into the study even if repeat measures may be under 10mIU/mL. 5. Ability to take the transdermal estradiol medication and be willing to adhere to the treatment regimen 6. Ability to complete the primary endpoint testing in English. Non-English speakers may be recruited if the participant is capable of performing the English version of the tests. Exclusion Criteria: 1. Spontaneous thelarche with breast Tanner stage 3 or more, spontaneous menarche or history of abnormal uterine bleeding. 2. Previous estrogen exposure 3. Cognitive impairment is severe enough to prevent assessment of the primary outcome measures. 4. Untreated hypothyroidism or celiac disease: Individuals may be recruited if on treatment and stable medication dose in past 3 months. 5. Subjects known to have Y-chromosome material unless they have undergone gonadectomy and have fully external female genitalia 6. History of any type of malignancy 7. History of a known clotting disorder/deep venous thrombosis 8. Any clinically significant abnormality as determined by the principal investigator.