During the decrease of menstrual cycles Estrogen levels decrease markedly, giving way to what is known as "hormonal deprivation "To osteoblasts and continuity to osteoclasts.
During this process there is an increase in osteoclastic activity in response to estrogen decrease and greater sensitivity to interleukin. The increase in osteoclastic activity can not be compensated for by osteoblastic activity, leading to a negative balance in bone turnover and consequently to osteoporosis , mainly affecting the trabecular bone (wrist and vertebrae).
This type of osteoporosis is called by some as type I osteoporosis, although the appropriate concept is hormone dependent or perimenopausal.
(Source: "Osteoporosis of the cell to the patient", Bulletin of the medical school Vol 29, No 1-2, 2000, Universidad Católica de Chile)