Complete Pubertal Induction
While the standard therapeutic regimen for pubertal induction in boys with HH based on testosterone administration has largely neglected testicular growth and spermatogenesis, this comprehensive prospective study demonstrates that induction of complete puberty including testicular maturation can be achieved by gonadotropin substitution. In addition, our observations confirm that pubertal virilization can be induced with gonadotropins without major adverse effects and with attainment of final heights in the range of mid-parental expectations in boys with HH of various origins.
We hereby suggest a protocol for hCG/rFSH replacement in prepubertal boys and testosterone-virilized adolescents with HH that is effective, irrespective of the underlying aetiology. While protocol B (aiming at testicular maturation after completed virilization) is comparable to regimens previously described for adults,[1,3,4] protocol A was established for complete pubertal induction in prepubertal boys, allowing for developmental immaturity (including delayed bone age) and aiming to achieve physiologic pubertal increments in serum testosterone levels during the first year of hormone replacement via progressive hCG dose escalation.
Differential Diagnosis of CDGP
The suggested protocol A enables activation of the pubertal GnRH pulse generator in cases of unrecognized constitutional delay of puberty (CDGP) by the use of low initial hCG doses, exerting only minimal suppressive effects on the hypothalamo–pituitary–gonadal (HPG) axis. We thereby identified two patients wrongly diagnosed with HH. Nevertheless, special attention to LH levels during gonadotropin replacement seems mandatory in view of this challenging differential diagnosis.
Somatic Outcomes (Primary Study End-points) and Duration of Gonadotropin Replacement
The findings of this study provide evidence that pubertal virilization, in concert with pubertal testicular growth and initiation of spermatogenesis, can be successfully induced during adolescence, with >72% normal (adult) final testicular sizes and >92% evidence of full spermatogenesis achieved by combined treatment with hCG and rFSH. Treatment for 6 months with hCG, followed by 25 months with rFSH, that is around 2·5 years of gonadotropin administration seems to be required in adolescents to tap the full individual potential for testicular growth and spermatogenesis.
Previous Studies on Adolescents
Previous studies, including a small number of prepubertal HH boys, have demonstrated the 'proof of principle' that hCG induces a rise in serum testosterone levels, resulting in virilization,[8,10,18,19] and that hCG combined with FSH stimulates testicular growth and activates spermatogenesis in adolescents.[6–11] Table 2 provides an overview on these studies, in comparison with our study.
The efficacy and safety of gonadotropin substitution in adult male HH patients for initiating testicular growth and spermatogenesis, sufficient for fertility, has been reported on several occasions.[1–4] HCG contains almost exclusively LH-like bioactivity, stimulating testosterone production by Leydig cells; FSH is required for spermatid maturation (spermogenesis) during the initiation, and for maintenance of quantitatively normal spermatogenesis at puberty and thereafter.[21,22] HCG has been used as a source of LH since 1952 and urinary human menopausal gonadotropin (hMG), applied to substitute for FSH since 1966.[1,2,6,7,24] Highly purified urinary FSH has been available since 1997/1998,[2,4] and recombinant FSH (rFSH) since 1995.[5,25–27] In this study, rFSH was used, as it is the only FSH preparation licensed for fertility induction in hypogonadotropic males in Europe.
Arguments for Conventional Pubertal Induction in HH
An argument that has been raised in favour of the traditional replacement regimen using testosterone-enanthate for puberty induction in HH is the practicability of one (or two)-month i.m. injections and the low costs of this replacement strategy. While the expenses of urinary-derived hCG replacement are comparable, rFSH is expensive. Another reason for compliance with testosterone is related to the assumption that fertility is 'not yet an issue' at an adolescent age and that the current strategy is satisfactorily addressing the patient's needs in terms of masculinity.
Impact of Gonadotropin Replacement on Quality of Life
Our results of QoL assessment pregonadotropin treatment demonstrate that the feeling of 'being different' in terms of sexual development at a time when normal puberty occurs has a negative impact on the young HH patient's well-being. Higher pretreatment depression scores in boys who had previously received testosterone for puberty induction (group B), compared to testosterone-naïve boys (group A) indicate that replacement of testosterone does not resolve this problem. Boys with HH do have pervasive and persistent concerns with body image and future fertility prospects. In support of this, a recent paper identifying unmet health needs of CHH patients based on a web-based assessment found that these individuals often struggle with the psychosocial sequelae of CHH. Our study provides evidence for reduced anxiety and improved overall QoL parameters, when physical pubertal normality is achieved, and when the potential for future fatherhood is demonstrated by activated spermatogenesis.
Although satisfaction with testicular size was remarkably higher after gonadotropin replacement in both treatment groups, we observed lesser final satisfaction with masculinity and persistently higher depression scores, even after treatment, in group B. Previous induction of incomplete puberty by testosterone thus seems to neglect a 'window of opportunity' to provide self-assurance and promote confidence for the future. Body image and fertility concerns in the HH patient may therefore best be addressed at a peer-related time. In support of this, overall compliance of study patients with taking five s.c. injections per week was surprisingly good and even better in previously prepubertal boys who were still under parental supervision.
Comparison of Adolescent Outcomes With Those of Adults
However, higher sperm concentrations achieved by adolescents may only be a relative advantage as spermatozoa of HH patients treated with gonadotropins or GnRH have an excellent fertilizing potential, despite subnormal counts.[3,8,29–31]
Impact of Previous Testosterone Replacement on Somatic Outcomes
Our study contributes to the question whether treatment effects of gonadotropins during adolescence are affected by previous testosterone replacement. In line with a recent meta-analysis of previous adult studies, which showed no significant association between prevalence of previous testosterone replacement and sperm concentration, we did not observe differences in outcomes with hCG/FSH replacement in terms of testicular size or sperm count achieved in prepubertal boys vs adolescents with prior full-dose testosterone replacement for up to 5·7 years. Only one of three patients who remained azoospermic had previously received testosterone. In contrast, in another study on adult patients that were previously treated with androgens, a decreased likelihood of achieving sperm output thresholds and conception was observed.
Factors Influencing Therapeutic Response to Gonadotropins
The results of this study indicate that testicular growth potential and achievable sperm concentrations in response to gonadotropin substitution during adolescence depend on various factors at baseline. Patients without previous bilateral cryptorchidism, with non-congenital HH causes, with higher baseline testicular volumes, and with higher baseline inhibin B and AMH serum levels had more favourable outcomes. These findings are in line with predictors of response to treatment that have been defined in adult studies.[3,26,29,31,34–36] All the above-mentioned parameters reflect the degree of seminiferous tubular maturation that may have occurred pretreatment, which in turn is dependent on the onset and the extent of GnRH and/or gonadotropin deficiency. However, as responses also depend on adherence to treatment, individual outcomes cannot reliably be predicted. The variability in observed response within certain diagnostic subgroups (Kallmann syndrome, CHH, MPHD congenital) may also be due to genetic heterogeneity and oligogenicity or epigenetic phenomena, resulting in different hormone secretion patterns, varying from complete absence of pulses to disorders of amplitude and/or frequency.
Further Arguments for Early Gonadotropin Substitution
Timely completed testicular maturation has further considerable advantages: First, it is likely to significantly reduce the time necessary for re-induction of spermatogenesis by future gonadotropin cycles in adulthood,[3,31] thereby enabling earlier spontaneous conception of the partner. This seems important in view of increasing female age at first pregnancy in modern societies. Second, poor responders to gonadotropin replacement during adolescence may respond worse with increasing age. Our adolescents were therefore given the opportunity for sperm cryopreservation, thereby safeguarding a chance for future biological paternity in case of adverse future events concerning fertility. Third, adolescents with persisting azoospermia may undergo mTESE before switching to permanent testosterone replacement and thereby rescue sperm for potential use in future reproduction. This was successfully performed in one patient in our study.
Questions remain as to the optimal timing of treatment with FSH and whether an attempt should be made to expand Sertoli cell numbers, either during the neonatal period (if HH is recognized by the presence of micropenis and cryptorchidism) or before initiating puberty and whether these actions could improve fertility. In a recent study, 7 adult HH patients without cryptorchidism given FSH treatment before GnRH substitution had serial testicular biopsies showing Sertoli and spermatogonial cell proliferation and higher final sperm counts than in the control group. However, final SCs were far below the normal range (5·8 ± 2·3 mill/ml).
Clin Endocrinol. 2017;86(1):75-87. © 2017 Blackwell Publishing