As a contraceptive, it works primarily by preventing ovulation and closing off the cervix to prevent the passage of sperm. The endometrial transformation dose of levonorgestrel is 150 to 250 μg/day or 2.5 to 6 mg per cycle.Due to its progestogenic activity, levonorgestrel has antigonadotropic effects and is able to suppress the secretion of the gonadotropins, luteinizing hormone and follicle-stimulating hormone, from the pituitary gland. This in turn, results in suppression of gonadal activity, including reduction of fertility and gonadal sex hormone production in both women and men. The ovulation-inhibiting dose of levonorgestrel in premenopausal women is 50 to 60 μg/day.In men, levonorgestrel causes marked suppression of circulating testosterone levels secondary to its antigonadotropic effects. In healthy young men, levonorgestrel alone at a dose of 120 to 240 μg/day orally for 2 weeks suppressed testosterone levels from ~450 ng/dL to ~248 ng/dL (–45%). Because of its effects on testosterone levels, and due to its androgenic activity being only weak and hence insufficient for purposes of androgen replacement in males, levonorgestrel has potent functional antiandrogenic effects in men. Consequently, it is able to produce adverse effects like decreased libido and erectile dysfunction, among others. In relation to this, levonorgestrel has been combined with an androgen like testosterone or dihydrotestosterone when it has been studied as a hormonal contraceptive in men. Androgenic activity
Levonorgestrel is a weak agonist of the androgen receptor (AR), the main biological target of the androgen sex hormone testosterone.
A hormone-receptor-positive (HR+) tumor is a tumor which consists of cells that express receptors for certain hormones. The term most commonly refers to estrogen receptor positive tumors (i.e. tumors that contain estrogen receptor positive cells), but can also include progesterone receptor positive tumors. Estrogen-receptor-positive tumors depend on the presence of estrogen for ongoing proliferation. Classification
ER-positive is one of the Receptor statuses identified in the classification of breast cancer. Receptor status was traditionally considered by reviewing each individual receptor (ER, PR, her2) in turn, but newer approaches look at these together, along with the tumor grade, to categorize breast cancer into several conceptual molecular classes that have different prognoses and may have different responses to specific therapies. DNA microarrays have assisted this approach. Diagnosis
Treatment
Endocrine treatment may be beneficial for patients with hormone receptor positive breast tumors.There are two ways for treating these kind of tumors: 

Lowering systemic levels of estrogen, achieved by the use of drugs from the aromatase inhibitor category. These drugs target one of the enzymes that takes part in the biosynthesis of estrogen. Blockage of the estrogen receptors on the cancerous cells, thus preventing estrogen binding, leading to decreased proliferation. Drugs in this category are also referred to as SERMs (Selective estrogen receptor modulator) since they are able to block estrogen receptors in a selective manner. See also
Tamoxifen
Raloxifene
Triple-negative breast cancer

References
Further reading
http://www.breastcancer.org/treatment/hormonal/what_is_it/hormone_role.jsp