Polymorphisms in <i>JMJD1C</i> are associated with pubertal onset in boys and reproductive function in men

Abstract JMJD1C, a member of the Jumonji-domain containing histone demethylases protein family, has been associated with levels of sex-hormone binding globulin (SHBG) and testosterone in men, and knock-out rodent models show age-dependent infertility. The objective of this study was to investigate whether single nucleotide polymorphisms (SNPs) nearby JMJD1C are associated with pubertal onset in boys and with male reproduction. 671 peri-pubertal boys, 1,027 young men, 315 fertile men, and 252 infertile men were genotyped for two JMJD1C SNPs (rs7910927 and rs10822184). rs7910927 and rs10822184 showed high linkage. Boys with the rs7910927 TT genotype entered puberty 3.6 months earlier than their peers (p = 2.5 × 10−2). In young men, the number of T alleles was associated with decreased levels of SHBG, follicle-stimulating hormone (FSH), testosterone, and testosterone x luteinizing hormone, as well as increased levels of Inhibin B, Inhibin B/FSH ratio, and testis size. No significant associations with semen parameters were observed and the genotype distribution was comparable among fertile and infertile men. In conclusion, genetic variation in the vicinity of JMJD1C had a surprisingly large impact on the age at pubertal onset in boys as well as levels of reproductive hormones and testis size in men, emphasizing the relationship between JMJD1C and reproductive functions

Development and validation of a mass spectrometry-based assay for quantification of insulin-like factor 3 in human serum

BACKGROUND: The circulating level of the peptide hormone insulin-like factor 3 (INSL3) is a promising diagnostic marker reflecting Leydig cell function in the male. Few commercial immunoassays of varying quality exist. Therefore, we decided to develop and validate a precise method for quantification of INSL3 by mass spectrometry. METHODS: We developed an assay in which the INSL3 A-chain is released from the INSL3 A-B heterodimer by chemical reduction and alkylation. The alkylated INSL3 A-chain is quantitated by liquid chromatography-tandem mass spectrometry (LC-MS/MS), as substitute for serum INSL3. The method was compared to a validated and sensitive in-house serum INSL3 immunoassay using 97 serum samples from 12 healthy boys during pubertal transition. Adult levels were determined based on sera from 72 adult healthy males aged 18-40 years. RESULTS: An LC-MS/MS assay with limit of detection and limit of quantification (LOQ) of 0.06 and 0.15 ng/mL, respectively, and intra-assay CVs <9% in the relevant ranges was obtained. The LC-MS/MS compared well with the in-house immunoassay (Deming regression slope: 1.28; Pearson correlation: R=0.86). INSL3 concentrations increased with pubertal maturation in healthy boys. INSL3 concentrations were above the LOQ in all samples from the adult men. The mean (±2 SD range)for serum INSL3 concentrations in the adult men was 2.2 (0.5-3.9) ng/mL. CONCLUSIONS: We have developed a robust and sensitive method suitable for quantitation of serum INSL3 in a clinical setting using LC-MS/MS instrumentation available in modern clinical laboratories. The method paves the way for future studies into the clinical role of serum INSL3 measurements

<i>UGT2B17</i> genotype and the pharmacokinetic serum profile of testosterone during substitution therapy with testosterone undecanoate. A retrospective experience from 207 men with hypogonadism

Background: Testosterone (T) is mainly excreted in the urine as testosterone glucuronide (TG). This glucuronidation is partly dependent on the UGT2B17 genotype, and TG excretion is therefore lower in men having the UGT2B17 deletion. However, the possible influence of UGT2B17 genotype on serum T during androgen therapy is unknown. We retrospectively investigated the possible association between the UGT2B17 gene polymorphism and serum T levels in hypogonadal men during Testosterone undecanoate (TU) substitution therapy. Subjects and Methods: Two hundred and seven patients treated with TU (Nebido(®)) were genotyped by quantitative polymerase chain reaction for the UGT2B17 deletion polymorphism. All were given 1000 mg TU per injection at 0, 6, and 18 weeks. Blood samples were taken 2 and 6 weeks after the first and second injection, prior to the third injection, and after 2–3 years of treatment. We analyzed for the levels of T, luteinizing hormone (LH), sex-hormone-binding globulin, estradiol, prostate specific antigen, hematocrit, hemoglobin, and total cholesterol. Results: The UGT2B17 genotype frequency was: ins/ins: 42%, ins/del: 44%, and del/del: 14%. During the initial 18 weeks of TU treatment, large intra- and inter-individual variations in serum T levels were observed. Large peaks in T levels, ranging from 6.7 to 69.5 nmol/l, were noted 2 weeks after injections, regardless of the genotype. T levels did not differ between the three genotypes prior to the third injection, but the del/del group had significantly lower levels of LH. At follow-up after 2–3 years, the injection interval or daily T dosage was not dependent on the UGT2B17 genotype. Conclusion: In conclusion, we found large intra- and inter-individual variations in serum T during standard TU treatment regimen in hypogonadal men. Only subtle differences in serum T and LH were noted according to UGT2B17 genotype, which however suggest that the UGT2B17 genotype exert modest influence on the pharmacokinetic profile of T after TU treatment