Discussion
REGRESSION
The present study demonstrated significant differences in the evolution of densitometric parameters between healthy adolescent non-COC users and the two groups of COC users over the same two-year follow-up period. In contrast to adolescents of the COC1 and COC2 groups, those of the control group exhibited an increase in BMD and BMC at all sites analyzed (lumbar, subtotal, and total body). In particular, a reduction in lumbar BMC and BMD was observed in the COC2 group. These results indicate that adolescent COC users do not exhibit the same bone mass acquisition during a period of life that is considered extremely important for bone acquisition, compromising the window of opportunity and possibly resulting in irreversible damage in future years [A Canadian prospective multicenter study included young adults and adolescents. Despite its multicenter design, the final sample did not differ from the number of adolescents included in the current study (168 adolescents). The participants were followed up for two years and COC users showed lower BMD gain than controls, but the difference was not significant. Losses to follow-up over time and different combinations and doses of the hormonal components may explain the nonsignificant and less relevant results compared to those observed in our study [The results of the present study corroborate data of a recent systematic review with meta-analysis regarding the lumbar site [Despite the difference in design compared to the present study, Cibula et al., in a prospective cross-over study with a control group and two groups of users (EE 30 and 15 μg), showed that the effect of contraceptives on the increase in bone mass was negative, preventing users from obtaining the expected bone acquisition, as observed in controls [It should be noted that our study design is based on strict inclusion criteria for all adolescents in the sample. This fact can increase the risk of loss to follow-up over a long observation period, in this case 24 months, which was observed in the three groups studied. The CHOICE study highlights that only 46.7% of adolescents aged 14 to 19 years continue to use hormonal contraceptives for more than 6 to 12 months [Despite the high percentage of losses in the groups after 24 months of follow-up described above, an analysis between the adolescents who remained in the study compared to those who were excluded showed no difference between the parameters studied, ruling out interference or bias in the results.Assessment of BMD is a static parameter and, therefore, does not reflect dynamic changes in bone tissue occurring at the time of measurement or shortly before. Bone resorption and formation are intimately linked processes in bone remodeling and estrogen is an important regulator of both processes [However, Gargano et al. did not identify differences in the effects of formulations containing EE, 20 or 30 mcg, both with added Drospirenone, on bone metabolism [Comparing different progestogens, Nappi et al. observed a greater reduction in bone marker concentrations in the Drospirenone group compared to the Gestodene group, a progestin of the same generation as the Desogestrel used in our study [Callegari et al. evaluated young women aged 16 to 25 years and identified the influence of contraceptives on markers of bone formation (P1NP) and resorption (carboxy-terminal telopeptide, CTX). The results showed concentrations 22% lower than those observed in non-users of hormonal contraceptives [Studies investigating bone markers in adolescence related to the use of contraceptives are still scarce in the scientific literature. Within this context, the results of the present study intend to contribute to the understanding of bone turnover in these adolescent users. The higher concentrations of bone formation markers at baseline observed in the control group (The current discussion is centered around the question of whether a reduction in the estrogenic component of oral contraceptives would have a negative impact on the bone health of adolescents, including reduced bone metabolism, since some studies point to a not yet defined ideal/physiological concentration of endogenous estrogen (window of action) that would exert an optimal effect on bone remodeling and peak bone mass [Although the present study presents some limitations, such as the loss to follow- up of some adolescents, an analysis of the power of the test for the comparison of the variation in mean absolute values for the outcomes lumbar spine, total body BMD, total body BMC, subtotal BMC between groups, using ANOVA with fixed effects, presented in Despite the difference in the number of participants between the groups, at the initial moment, the groups demonstrated homogeneity in the majority of the variables analyzed (Furthermore, multiple linear regression analyses were performed, with adjustments for possible confounders, such as bone age, total body BMD, and BMI at baseline, indicating that statistical differences were maintained (