Enobosarm and Anastrozole in Pre-menopausal Women With High Mammographic Breast Density

Inclusion Criteria: * Provision of written informed consent * Pre-menopausal levels of FSH/LH/E2 (follicle stimulating hormone, luteinizing hormone, oestrogen) according to the definition of "pre-menopausal range" for the laboratory involved * Have a Volpara Density volumetric breast density of \>15.5% (combined average both breasts) * Breast pain in the previous month of equal to or greater than 40mm on a 100mm visual analogue pain scale * WBC ≥ 3.0 x 109/L, granulocytes ≥ 1.5 X 109/L and platelets ≥ 100 x 109/L. * AST/SGOT or ALT/SGPT ≤ 3 times ULN * eGFR\> 60 ml/min/1.73m2 * Negative pregnancy test in women of childbearing potential (premenopausal or less than 12 months of amenorrhea post-menopause, and who have not undergone surgical sterilization), no more than 7 days before the first dose of study treatment; * For women of childbearing potential who are sexually active, agreement to use a highly effective, non-hormonal form of contraception during and for at least 6 months after completion of study treatment; OR, a fertile male partner willing and able to use effective non-hormonal means of contraception (barrier method of contraception in conjunction with spermicidal jelly, or surgical sterilization) during and for at least 6 months after completion of study treatment; Exclusion Criteria: * Presence of breast cancer * Diabetes mellitus or glucose intolerance defined as a fasting glucose \>6mmol/l * Previous or concomitant other (non-breast cancer) malignancy within the previous 5 years (other than skin cancer) * History of coronary artery disease * Systemic hormonal contraception * Risk of transmitting Human Immunodeficiency Virus or viral hepatitis via infected blood * Known hypersensitivity to any component of testosterone * Unable to comply with study requirements * Prolonged systemic corticosteroid treatment * Any investigational drugs * Systemic hormone replacement therapy * Pregnant or lactating women * Known liver disease * Current warfarin usage