Endocrine Abstracts

Background: Osteoprotegerin (OPG), a component of the RANKL/RANK/OPG pathway, can inhibit bone resorption by affecting osteoclastogenesis. Estrogens deficiency is associated with decreased expression of OPG and increased osteoclast activity, and thus can lead to disorders of bone remodeling.

Objective: To analyze relationship between serum OPG and bone mineral density (BMD) in patients with Turner syndrome (TS) subjected to estroprogestagen (EP) treatment.

Material and methods: The study included 44 patients with TS, aged between 16 and 28 years. All the patients were characterized by short stature, lacked any signs of puberty and primary amenorrhea, and had no history of treatment with EP, GH and anabolic preparations. Therefore, they represented natural model of clinical hypoestrogenism. We monitored hormonal parameters (TSH, fT₄, FSH, LH, E₂, T) of the participants, along with their bone turnover marker levels (BALP, Ntx) and bone mineral density (BMD). Furthermore, OPG concentration was determined prior to and after 6 months and 2 years of EP treatment.

Results: The average increase in BMD amounted to 7.5%±10.9 and 6.6%±9.5 g/cm² after the first and the second year of treatment respectively. However, BMD documented after 2 years of hormonal treatment did not differ significantly from its pretreatment level. The baseline concentration of OPG amounted to 4.52±0.79 pmol/l, and its concentrations measured after 6 months and 2 years of EP treatment equaled 6.47±1.64 pmol/l (P<0.01) and 4.39±0.78 pmol/l (P>0.05) respectively.

Conclusion: Although increased endogenous synthesis of OPG is considered a therapeutic target in patients with reduced bone mineral density, we did not observe significant increase in BMD after 2 years of estroprogestagen treatment, and concentration of OPG returned to its pre-treatment levels. This suggests that estrogens exert limited effect on osteoprotegerin expression.