The main finding of this study is the improvement in sexual function after the implantation of non-hormonal LARCs, especially SIUD, and the worsening of sexual function in patients after ENG implantation involving the use of two instruments. The QS-F was developed specifically for the Brazilian female population. However, the FSFI is an instrument consolidated internationally and the use of both tools increased the study reliability, since both instruments showed the same outcome.
Most women evaluated in this study consider it very or extremely important that the contraceptive method chosen does not change their libido or interrupt the sexual act. This, together with the effectiveness of the method, were the most important reasons for choosing the contraceptive method in the groups evaluated, reflecting the great importance given by patients to maintain sexual function. Assessing female sexual function is important, as it interferes with quality of life and is generally associated with general health issues (25). Abdo et al. (19) show that 49% of Brazilian women have some degree of sexual dysfunction, including decreased libido, dyspareunia, or dysfunctional orgasm. This study did not assess the prevalence of sexual dysfunction for the methods evaluated, but rather the sexual function changes resulting from LARC implantation.
Intrauterine devices that combine silver and copper began to be used in the USA in the 1970s, showing lower pregnancy rates when compared to devices only containing copper (26).The addition of silver to the device aimed at preventing corrosion (27), with copper release seeming to remain unchanged when silver is added (27, 28). Although the combined use of copper and silver is already well established in many countries, in Brazil, this device started to be marketed in 2016 under the name Andalan Silverflex®. To date, no study was found comparing sexual function changes in SIUD and classic devices users without the incorporation of silver. Our study shows that non-hormonal devices improve sexual function when compared to hormonal devices, especially in the domain related to sexual desire, and SIUD seems to show even more significant improvement when compared to CuIUD, since it shows a statistically significant total score improvement of sexual function with both instruments used.
Despite studies showing that the use of contraceptives increases libido in women with decreasing concerns about an unwanted pregnancy (29), this study shows a worsened sexual function, including libido, with ENG. The literature presents conflicting results regarding the influence of ENG on sexual function. As described by Bason (2001), the female sexual response is complex, because it is influenced by a multifactorial factors including biological, psychological and sociocultural (30). The psychological factor was analyzed in a study that demonstrated decreased vitality and emotional function in patients in the first three months of ENG use (31). However, this study reported no worsening of sexual function in the group studied. The study by Bozalis et al. (2016), based on a large database (CHOICE), showed that ENG users reported the loss of sexual interest more frequently when compared to CuIUD users (9). Two studies evaluating the side effects of ENG use in women followed up for about two years show a prevalence of 2.5% and 1.6% decreased libido, respectively (32, 33). Decreased libido was associated not only with ENG, but also with depot medroxyprogesterone acetate (DMPA) injections, which may be related to systemic progestin release (9, 34). Estrogens have a fundamental role in female sexuality and their administration can be a recommended treatment for low libido and hypoactive sexual desire disorder (35). Systemic progestins can suppress ovarian function and consequently decrease the natural production of estrogen, resulting in loss of sexual desire (9). In addition, ENG is the device with the highest rate of discontinuation among LARCs users (36). In the present study, five (29%) of the 17 ENG users discontinued the method within six months after the second stage of the study (data not shown). Some studies associated the discontinuation of LARCs with sexual function changes (12, 37, 38), suggesting a negative effect of ENG on sexual function.
This study also correlated metabolic and hormonal parameters with sexual function findings. Total testosterone levels increased in non-hormonal LARCs users and remained constant in hormonal LARCs users. These results may be related to the fact that some women in this study were using combined oral contraceptive methods before starting LARC implantation, which is known to reduce total testosterone (39, 40). Since SIUD and CuIUD contain no hormones, their use would make it possible to re-establish the androgen production axis, whereas, for hormonal LARCs, this re-establishment could occur partially or not occur. The decreased SGBH in all groups in this study may also be due to the use of combined oral contraceptives prior to LARC implantation. The LARC agents are known increase the hepatic production of SHBG (39, 40). Many studies suggest that this is one of the reasons why the use of combined oral contraceptives reduce libido, since excess SBGH would decrease the free testosterone fraction in women, directly affecting sexual function (14, 15). In addition, the fact that the higher levels of total testosterone observed in users of non-hormonal LARCs could also be related to improved sexual function in these groups cannot be excluded.
The increased hemoglobin levels observed in women using the LNG and ENG progestin hormonal methods in this study corroborates other studies (41, 42). Likewise, reduced hemoglobin levels in CuIUD were already analyzed in many studies (43, 44). The SIUD group, however, presented a slight non-significant hemoglobin increase, which may mean a better SIUD response compared to CuIUD regarding blood loss. These data could be related to the smaller copper surface covering the SIUD, generating less inflammatory reaction and, therefore, less bleeding during the menstrual period (45).
This present study observed decreased prolactin levels in all groups evaluated, but with a statistically significant reduction only for non-hormonal LARCs. Once again, the use of combined oral contraceptives may have influenced these results. Prolactin levels has been studied for non-hormonal LARCs since the 1970s, and these studies report that these devices cannot influence the plasma levels of this hormone (46, 47). However, ethinyl estradiol and levonorgestrel oral contraceptives presented a considerably increased prolactin and macroprolactin plasma levels (48, 49). Thus, the discontinuation of oral contraceptives through the implantation of LARCs could re-establish baseline levels, especially with the use of non-hormonal LARCs. Another factor that could interfere with serum prolactin levels is pulsatility, since these levels vary within the normal range throughout the ovulatory cycle, reaching a maximum of 20 ng/ml near ovulation (50). Slightly increased T4 baseline levels were observed for LNG, but TSH levels remained unchanged in this group, suggesting that this change may be unimportant. Lipid parameters seemed to be stable after LARC implantation, which corroborates the literature (51).