Influence Of Gene Mutations On Hypothalamus Pituitary Gonad Axis Function And Gonadotropin Induced Spermatogenesis In Male Patients With Idiopathic Hypogonadotropic Hypogonadism

ObjectiveThe aims of our study were as followings:(1) To clarify the incidence of bigenic and monogenic mutations in Chinese male patients with IHH.(2) To investigate the relationship between genotype and phenotype in some IHH patients with known gene mutations.(3) To evaluate the influence of gene mutations and clinical features (anosmia) on gonadotropin induced spermatogenesis.(4)To explore the predictive factors (clinical features and gene mutations) for patients with reversed gonad axis function.Methodes(1) Molecular studies:A gene chip (NimbleGen2.1M) and high-throughput techniques were used to investigate the mutations in19IHH genes of male IHH patients. For each mutants, the possible SNPs or pathogenic role was evaluated by four data banks (dbSNP, Hapmap,1000genes, BGI local gene bank). The SIFT and Polyphen-2, two widely used computer simulated software, were used to predict the degree of impaired protein function. For the definite gene mutants, classical direct PCR method was used to confirm the results. The patients were classified into four groups according to their gene results:definite mutation group, suspected mutation group, invalid mutation group and no known mutation group.(2) Clinical studies:the clinical data of IHH patients were collected from the medical records, including the age, testicular volumes, cryptorchid history, other secreted hormones from the pituitary gland, magnetic image of olfactory bulb and the effects of gonadotropin induced spermatogenesis. A spermatogenesis score system, including testicular volumns, testosterone levels responsing to HCG, sperm count and other important parameters, reflects the effets of gonadotropin induced spermatogenesis. The score was semiquantitatively defined as0,1,2and3. The higher the score, the greater capacity for sperm production.(3) Data analysis:Unpaired t test were used to compare the difference between two groups comprising normal distributed continuous variable. Kruskal-Wallis was used to compare the difference between two groups comprising normal distributed uncontinuous categorical variables.Results(1) In our male IHH patients,87/259patients (33.6%) were found had known definit gene mutations. The percentage of suspected mutations, invalid mutations and no known mutations were13.5%,26.8%and26.2%, respectively. The percentage of definite gene mutations were as followings:CHD719.1%, FGF82.2%, FGFR122.5%, GNRHR4.5%, KAL115.7%, KISS1R2.2%, LEPRE1.1%, LHB3.4%, NELF1.1%, PROK24.5%, PROKR221.3%and WDR111.1%. No mutations were detected in DAX1, Leptin, FSHB, TACR3/TAC3, PCSK1and GNRH1. CHD7, FGFR1, KAL1and PROKR2dominated79%of all definite gene mutations.(2) In patients with definite gene mutations, two patients (2.2%) had trigenic mutations,18(20.7%) had bigenic mutations, and67(77.0%) had monogenic mutations. No significant differences were found in the testicular volumns and gonadotropin induced spermatogenesis scores between oligo-and mono-genic mutation groups.(3) The patients with FGFR1mutation had higher incidence of cryptorchid, lower spermatogenesis score than patients with other gene mutations. Spermatogenesis score was lower in definite mutation group than suspected mutation group (0.99±0.08vs.1.47±0.14,P=0.003) and no known gene mutation group (0.99±0.08vs.1.37±0.10, P=0.003). Spermatogenesis score of nIHH from definite gene mutation group was lower than that from no known mutation group (1.09±0.13vs.1.70±0.10, P=0.0006), while the score of KS had no significant difference between gene mutation-positive group and no known mutation group. In general, the spermatogenesis score from the lowest to the highest were as followings:FGFR1mutation group<KS and definite gene mutation group<nIHH from no known mutation group.(3) The patients with positive family histories have a tendency for KAL1mutation. The patients with FGFR1mutation may present with short status, plate clips and tooth aplasia. KAL1and CHD7mutation may cause unilateral renal dysplasia. However, these clinical features can also been seen in patients from no known mutation group.(4) Seven IHH patients (2.7%) had reversal of gonad axis function. Among them, four patients had gene mutations in KALI (2patients), PROKR2(1patient) and LHB (1patient). The average diagnostic and reversal age was22.4±0.8and25.1±0.7years. Their GnRHa stimulated LH level was19.1±2.2(7.7-33mIU/ml) and their initial testicular volume was6.0±0.6mL.Conclusions(1) Causative gene mutations can be detected in about1/3of IHH male patients. CHD7, FGFR1, PROK2and KAL1dominated79%of all mutations.(2) In patients with definite gene mutations,23%of them were oligogenic mutations and77%were monogenic mutations. The spermatogenesis scores had no significant difference between these two groups.(3) According to the genotypes and olfactory manefestations, the spermatogenesis scores from the lowest to the hightest were as followings:FGFR1mutation group<KS and definite mutation group<nIHH from no known mutation group.