The primary objective of this trial is to evaluate ovarian suppression following treatment with ZOLADEX 10.8 mg by luteinizing hormone (LH).
Gonadotropin-releasing Hormone (GnRH) treatment-naïve: Female participants aged 18 to 55 years, inclusive.
GnRH treatment-exposed <6 months: Female participants aged 18 to 55 years, inclusive, if GnRH treatment started within <6 months of signing the informed consent.
Advanced or metastatic breast cancer: Histological confirmation of breast cancer with evidence of locally advanced or metastatic disease, which is not amenable to surgical resection or radiation therapy with curative intent per investigator's assessment.
HR+: Either estrogen receptor positive (ER+) or progesterone receptor positive (PR+) breast cancer, defined as 1% to 100% of tumor nuclei are positive for ER or PR via immunohistochemistry.
Postmenopausal: Naturally or surgically postmenopausal (regardless of age).
Body mass index (BMI): <18 kg/m² or >35.0 kg/m².
Prior surgical or radiation procedures: History of bilateral oophorectomy or prior radiotherapy to the ovaries.
Radiotherapy for breast cancer within 4 weeks prior to trial enrollment.