In this cohort study, serum AMH was demonstrated to be a well-performed predictor for ovarian response in IHH patients. Compared with patients with a proper ovarian reserve function, a satisfied IVF outcome and lower OHSS occurrence were observed in IHH, providing the Gn dose reference for IVF treatment in the future. AMH levels were significantly lower in IHH patients, while the higher fertilization rate and the number of transferable embryos indicate that adequate gonadotropins could reboot the “dormant” status of antral follicles and nourish them to mature oocytes in IHH patients.
IHH, a rare genetic disorder, is characterized by a failure of GnRH secretion or action resulting in the inability to enter or progress through puberty and retaining sexual infantilism and infertility in the absence of exogenous hormone supplements (5, 6). Accurate interpretation of evidence-based clinical information and discovering efficient and safe Gn dosing are critical for current clinical care and counseling of patients with rare disorders in IVF treatment. However, owing to the rarity of IHH, only limited cohort studies were published before, and the management of women with IHH is still not standardized (7) with the difficulties in early identification and prompt transition of clinical care. Thus, the first aim of this study was to address the IVF outcomes in one of the largest cohorts with IHH and determine the valuable findings to further provide clinical curation of IHH.
As expected, IHH patients have observed higher Gn consumption and longer treatment duration with varied causes of infertility, including male factor, tubal factor, and unexplained factor, in line with previous reports (8–12). Despite the CP rate and LB rate being similar in IHH and matched control groups, the higher fertilization rate, ET rate and transferable embryos were validated in IHH patients in our study, which was against the previous study (9). This result suggests that the development and maturation of oocytes were temporally "switched off" instead of "cutting off" in IHH and could be aroused by the proper amount and sufficient treated period of pituitary hormone. In agreement with this point, the higher MaxE2/etotal and lower pregnancy loss rate (2.7%) in the IHH group were displayed in this study, which lowered from previous reports from different study groups with the declaration of pregnancy loss occurrence in 17.1–19.7% after IVF/ICSI (13–15). This finding highlights that women with IHH could potentially regain reproductive function and respond very well to exogenous gonadotropins with a high quality of oocytes/embryos. Thus, assessment of ovarian response in the IHH cohort to COS is of utmost importance for achieving satisfied IVF outcomes (i.e., ET rate and LB rate) and simultaneously avoiding COS-associated complications.
The next question that comes to mind is how to measure the ovarian response of patients with HH. Hypogonadism, ovarian infantilism and anovulation challenged the baseline test for hormonal levels and other ovarian response-related factors (i.e., AFC) in IHH. Although AMH is identified as a valuable marker of ovarian reserve in reproductive-aged women (16, 17), the debate on whether serum AMH could serve as a prognostic marker of fertility in IHH remains untacked. Despite a small sample size (n = 12), an earlier study proposed that AMH appears as a promising marker of ovarian response in patients with IHH undergoing IVF (18), which was consistent with this current study. However, the emerging evidence pointed out that AMH is fluctuated and is not gonadotropin-independent throughout folliculogenesis (19, 20). When priming with a period of Gn, the lower level of AMH in IHH women can be reversed by follicle-stimulating hormone (21), suggesting AMH levels may underestimate ovarian reserve due to the lack of FSH-dependent growing follicles. Thus, aware of the complexity of AMH dynamics, the current study with a fresh look, discovered a satisfactory ovarian response and highlighted that AMH was superior to other markers to predict either low or high response.
Nevertheless, AMH should be cautiously used in assessing the primordial follicle pool and prognosticating the outcome of IVF, especially in gonadotropin-deficient states. Low AMH in IHH should not be judged as a reflection of poor ovarian reserve, as gonadotropin administration can effectively restore fertility. The higher CP rate and LB rate in IHH with a high ovarian response may reflect the reversal in IHH, which means the patients with IHH later achieve activation of their hypothalamic-pituitary-gonadal axis with regain the ability in gametogenesis(22). These patients may retain partially active reproductive endocrine function or potential at the “dormant phase.” It is possible that the dynamic nature of the HPG axis renders them susceptible to exogenous gonadotropins supplement/stimulation (22, 23).
Interestingly, in univariate analyses of cycles in IHH-ET, a significant difference was observed in the iGn. Lower iGn was commonly used in the CP group in IHH, even though there was no difference in the distribution of patients with varied ovarian responses. In this study, the gonadotropin for starting the COS ranged from 150 IU to 300 IU (covering 84.8% of cases). A similar strategy pattern for iGn using a usual dosage (150 IU, 150 IU to 450 IU, and 315 IU) was presented in earlier studies(9–11). In comparison, another group attempted to start at 450 IU to 600 IU with a step-down regimen. The high dose of iGn did not come along with satisfying clinical outcomes, shortened Gn treatment, and decreased tGn. From this standpoint, the resurrection stage of the fertile status IHH comprises a series of adaptations as a "boiling frog in warm water" phenomenon.
Further analysis of the usage of Gn dosing in IHH-ET was performed to discover the core contributor to defining treatment management in clinical practice. AMH and patient age-based Gn dosing was commonly used in our infertility center, whereas AFC was more referred significantly to treatment duration. So far, under the present treated protocol, a satisfied IVF outcome was observed in the IHH cohort with a similar etotal, CP rate and LB rate compared with the non-IHH cohort. It was convinced that the pregnancy rate would climb by reaching the embryo transfer stage in an aged HH patient. It was no difference in the cancellation rate for the high risk of hyperstimulation in IHH and controls, yet only one patient with mild OHSS occurred in the IHH group. To retrieve adequate oocytes and avoid COS-related complications, individualized protocol raises attention to the clinic due to the effectiveness of treatment during IVF. Individualized dosing based on AMH or AFC reduced the occurrence of mild and moderate OHSS (24, 25). Therefore, more cohort study needs to be completed to estimate the power of individualized dosing protocol in IHH.
The strength of this study is the great benefit of the large size of the IHH cohort worldwide, allowing us to dissect the information from different aspects and to explore the population features in IVF procedure, including the ovarian response, CP outcomes and efficient Gn use. Notably, considering the unique biological nature of IHH, only the ultra-long GnRH-a protocol was discussed in the control group, inducing a hypogonadotropic state, which was absent in previous studies. Some limitations need to be addressed. First, owing to the concern of inherent biases of discrepancy of patients’ data in different cycles, the fact that only the first fresh cycle was investigated in this study is a potential weakness. The hormone supplement could reverse the hypo-status in IHH, and the impact would be heterogeneous in patients. Second, even though our results were convincing to provide a numerical Gn dose reference, the safety management of individualized dosing still needs more studies and data accumulation to give the ultimate answer.