The prevention and the treatment of oestrogen deficiency induced by breast cancer treatments are crucial in the management of patients. The impacts of this deficiency must not be neglected: quality of life impairments inducing eventually premature withdrawal of hormonotherapies, and excess of bone and cardio-vascular morbidities and mortalities, especially in good prognosis young women. Management strategies of short and long term effects of this deficiency are reviewed and discussed here.