Bone mass changes in patients treated for 6 months with GnRH analogues associated with a low dose of ERT as 'add-back' therapy

The role that GnRH analogues-induced hypoestrogenism has on the phospho- calcic metabolism and on the bone demineralization is stressed. Most of studies on this issue show a bone loss during GnRH analogues treatment in young and premenopausal women even often a 6 months therapy. The premature bone loss can induce an increase in osteoporotic risk in long term administration mostly in repeated cycles. Several drugs have been used in association with GnRH in order to achieve a bone protection during pituitary block without a growth of uterine leiomyomata and endometriotic foci or functional uterine bleeding. The aim of our study was to verify the osteoblastic activity and the modifications of the bone mass in a group of 60 women (ages 35-45 years) suffering from functional uterine bleeding and uterine leiomyomata, submitted to a pituitary block with GnRH analogues for a 6 months period. The patients were randomised in 3 groups including 20 women. As 'add-back' therapy the group 1 received Tibolone acetato (1tab./day for 6 months); the group 2 received transdermic estradiol (25 mg..twice weekly for 6 months); the group 3 received a placebo (1 tab./day for 6 months). The bone calcic content has been evaluated by osteosonografy (with DBM sonic 1200) and by serum assay of total alkaline phosphatase (ALK-Ph), osteocalcina (BPG) and hydroxy-prolinuria in 24 hours. Those controls have been carried out at the beginning, during at the end of the treatment and after 6 and 12 months. Our experience shows that in short term therapy (3 months) with GnRH analogues, Tibolone acetate and ERT give similar results on the bone metabolism. On the contrary in middle and long term therapy (6 months), and above all in repeated cycles with GnRH analogues, the 'add-back' therapy with low dosage ERT allows to achieve better results on the bone metabolism.