TRACK_9: Testosterone replacement assessment: Classical vs. functional hypogonadism­knowledge from a 9­year study

BACKGROUND AND OBJECTIVE: The longitudinal efficacy and clinical utility of Testosterone Therapy (TTh) in ameliorating functional hypogonadism (FH) remain contentious, with long-term data being scarce. To address this lacuna, a comprehensive long-term registry study, stratifying patients across a spectrum of hypogonadal etiologies, offers a robust investigative paradigm. MATERIALS AND METHODS: This 9-year registry, encompassing 650 patients (equivalent to 4,362 cumulative years of treatment), included 188 patients diagnosed with FH (mean age 42.3 ± 11.3 years) and 462 individuals with classical hypogonadism (CH). The cohort segregated into 266 men with primary hypogonadism (PH, mean age 34.0 ± 11.7 years) and 196 with secondary hypogonadism (SH, mean age 31.9 ± 12.0 years). Uniform treatment across the cohort involved intramuscular administration of testosterone undecanoate (1,000 mg). A comparative analysis was conducted focusing on anthropometric, metabolic, and safety parameters. RESULTS: Serum testosterone levels increased from 6.6 ± 2.4 to 19.3 ± 2.9 nmol/L (p < 0.001). TTh was linked with weight reduction and decreased waist circumference (WC) in both CH and FH cohorts (both p < 0.001). Cox regression and Kaplan-Meier analyses delineated disparities: men with FH demonstrated a higher propensity for losing > 10% body weight and > 5% WC compared to CH (hazard ratio [HR] 1.3 [1.1-1.4], p = 0.008 and HR 1.4 [1.3-1.5], p = 0.001). Increases in hematocrit > 50% were uniform across groups, albeit amelioration of anemia was more pronounced in FH versus CH (p = 0.002). Increments of prostate-specific antigen (PSA) levels were more likely to occur in FH (HR 1.3 [1.1-1.6], p = 0.003). FH patients exhibited pronounced improvements in metabolic parameters and in aging male symptom score (AMS) and IIEF-EF questionnaire scores. These effects were markedly modulated by age and initial weight. Subgroup analysis of age-matched obese patients revealed an accentuated impact of TTh in CH compared to FH. DISCUSSION AND CONCLUSION: The therapeutic outcomes of TTh across distinct hypogonadal populations demonstrate heterogeneous responses, significantly influenced by diagnostic categorization, age, and baseline risk factor profiles.

Human fertilization in vivo and in vitro requires the CatSper channel to initiate sperm hyperactivation.

The infertility of many couples rests on an enigmatic dysfunction of the man's sperm. To gain insight into the underlying pathomechanisms, we assessed the function of the sperm-specific multisubunit CatSper-channel complex in the sperm of almost 2,300 men undergoing a fertility workup, using a simple motility-based test. We identified a group of men with normal semen parameters but defective CatSper function. These men or couples failed to conceive naturally and upon medically assisted reproduction via intrauterine insemination and in vitro fertilization. Intracytoplasmic sperm injection (ICSI) was, ultimately, required to conceive a child. We revealed that the defective CatSper function was caused by variations in CATSPER genes. Moreover, we unveiled that CatSper-deficient human sperm were unable to undergo hyperactive motility and, therefore, failed to penetrate the egg coat. Thus, our study provides the experimental evidence that sperm hyperactivation is required for human fertilization, explaining the infertility of CatSper-deficient men and the need of ICSI for medically assisted reproduction. Finally, our study also revealed that defective CatSper function and ensuing failure to hyperactivate represents the most common cause of unexplained male infertility known thus far and that this sperm channelopathy can readily be diagnosed, enabling future evidence-based treatment of affected couples.

Genetic Architecture of Azoospermia-Time to Advance the Standard of Care.

BACKGROUND: Crypto- and azoospermia (very few/no sperm in the semen) are main contributors to male factor infertility. Genetic causes for spermatogenic failure (SPGF) include Klinefelter syndrome and Y-chromosomal azoospermia factor microdeletions, and CFTR mutations for obstructive azoospermia (OA). However, the majority of cases remain unexplained because monogenic causes are not analysed. OBJECTIVE: To elucidate the monogenic contribution to azoospermia by prospective exome sequencing and strict application of recent clinical guidelines. DESIGN, SETTING, AND PARTICIPANTS: Since January 2017, we studied crypto- and azoospermic men without chromosomal aberrations and Y-chromosomal microdeletions attending the Centre of Reproductive Medicine and Andrology, Münster. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: We performed exome sequencing in 647 men, analysed 60 genes having at least previous limited clinical validity, and strictly assessed variants according to clinical guidelines. RESULTS AND LIMITATIONS: Overall, 55 patients (8.5%) with diagnostic genetic variants were identified. Of these patients, 20 (3.1%) carried mutations in CFTR or ADGRG2, and were diagnosed with OA. In 35 patients (5.4%) with SPGF, mutations in 20 different genes were identified. According to ClinGen criteria, 19 of the SPGF genes now reach at least moderate clinical validity. As limitations, only one transcript per gene was considered, and the list of genes is increasing rapidly so cannot be exhaustive. CONCLUSIONS: The number of diagnostic genes in crypto-/azoospermia was almost doubled to 21 using exome-based analyses and clinical guidelines. Application of this procedure in routine diagnostics will significantly improve the diagnostic yield and clinical workup as the results indicate the success rate of testicular sperm extraction. PATIENT SUMMARY: When no sperm are found in the semen, a man cannot conceive naturally. The causes are often unknown, but genetics play a major role. We searched for genetic variants in a large group of patients and found causal mutations for one in 12 men; these predict the chances for fatherhood.

The HEAT-Registry (HEmatopoietic Affection by Testosterone): comparison of a transdermal gel vs long-acting intramuscular testosterone undecanoate in hypogonadal men.

CONTEXT: Testosterone (T) therapy of hypogonadal men requires stable kinetics, tolerance and attenuation of symptoms. Both intramuscular injections of the long-acting ester T undecanoate (TU) and transdermal application of T gel offer a proven efficacy. As T has marked effects on hematopoiesis, an elevation of hematocrit has to be considered during T therapy. OBJECTIVE: To compare the effects of a transdermal T gel with long-acting intramuscular TU on hematopoiesis, controlling for age, diagnosis, androgen receptor susceptibility and obesity. DESIGN: Prospective two-arm open registry, minimum duration of 26 weeks per patient. Putative modulators of erythropoiesis entering regression models were type of medication, type of hypogonadism, delta of total testosterone concentrations, waist circumference, age as well as (in a sub-group) androgen receptor gene CAG repeat length. SETTING: Tertiary university based andrological outpatient department. PATIENTS: 802 hypogonadal men, 498 receiving T gel and 304 receiving intramuscular TU, median age 40 years (interquartile range = 25). RESULTS: Follow-up visits after initiation of treatment occurred between treatment weeks 26-30. Serum T concentrations increased markedly in both patient groups. Men receiving intramuscular TU exhibited an increased hematocrit (>50%) to a significantly higher amount than men receiving T gel (69/304 vs. 25/498, p < 0.001). Corresponding results were seen for higher values of hematocrit (>52% and >54%). Advanced age (p = 0.009), higher waist circumference (p = 0.01), higher delta testosterone (p = 0.007) and functional vs classical hypogonadism (p = 0.04) contributed to the effect in stepwise multiple regression models. Attenuated androgen action (longer androgen receptor CAG repeats) mitigated the effect (p = 0.01) in a subgroup of 574 patients. Men with anemia (hemoglobin ≤12.7 g/dl) were more likely to move out of the pathological range when receiving TU vs T gel (41/53 vs. 49/89 p = 0.01). CONCLUSIONS: T substitution with intramuscular TU or T gel increase T concentrations effectively. Long-acting TU leads to a higher rate of hematocrit levels >50%, whilst at the same time it seems to be more efficient to ameliorate anemia in the subgroup of respectively affected hypogonadal patients . This applies especially to obese older men with functional hypogonadism.

Machine learning based prediction models in male reproductive health: Development of a proof-of-concept model for Klinefelter Syndrome in azoospermic patients.

BACKGROUND: Due to the highly variable clinical phenotype, Klinefelter Syndrome is underdiagnosed. OBJECTIVE: Assessment of supervised machine learning based prediction models for identification of Klinefelter Syndrome among azoospermic patients, and comparison to expert clinical evaluation. MATERIALS AND METHODS: Retrospective patient data (karyotype, age, height, weight, testis volume, follicle-stimulating hormone, luteinizing hormone, testosterone, estradiol, prolactin, semen pH and semen volume) collected between January 2005 and June 2019 were retrieved from a patient data bank of a University Centre. Models were trained, validated and benchmarked based on different supervised machine learning algorithms. Models were then tested on an independent, prospectively acquired set of patient data (between July 2019 and July 2020). Benchmarking against physicians was performed in addition. RESULTS: Based on average performance, support vector machines and CatBoost were particularly well-suited models, with 100% sensitivity and >93% specificity on the test dataset. Compared to a group of 18 expert clinicians, the machine learning models had significantly better median sensitivity (100% vs. 87.5%, p = 0.0455) and fared comparably with regards to specificity (90% vs. 89.9%, p = 0.4795), thereby possibly improving diagnosis rate. A Klinefelter Syndrome Score Calculator based on the prediction models is available on http://klinefelter-score-calculator.uni-muenster.de. DISCUSSION: Differentiating Klinefelter Syndrome patients from azoospermic patients with normal karyotype (46,XY) is a problem that can be solved with supervised machine learning techniques, improving patient care. CONCLUSIONS: Machine learning could improve the diagnostic rate of Klinefelter Syndrome among azoospermic patients, even more for less-experienced physicians.

Pituitary response to GnRH stimulation tests in different FSHB-211 G/T genotypes.

STUDY QUESTION: Does pituitary response to a GnRH stimulation test differ according to the different FSHB-211 G/T genotypes? SUMMARY ANSWER: The promoter polymorphism FSHB-211 G > T affects the pituitary response to exogenous GnRH stimulation by reducing FSH and increasing LH outputs. WHAT IS KNOWN ALREADY: The FSHB-211 G > T single nucleotide polymorphism (SNP) is known to affect pituitary FSH output by impairing the transcriptional activity of FSHB. STUDY DESIGN, SIZE, DURATION: This was a cross-sectional, retrospective study on 67 male subjects (mean age: 24.6 ± 10.3 years) undergoing a GnRH stimulation test for diagnostic purposes in cases of secondary hypogonadism. PARTICIPANTS/MATERIALS, SETTING, METHODS: A GnRH stimulation test was performed by administering an i.v. bolus of 100 µg of the GnRH-analogue gonadorelin acetate to all patients, with blood samples drawn from the cubital vein immediately prior to injection (T0) and 30 (T1) and 45 minutes (T2) after. Clinical and genetic data were retrieved from a computerized database. Linear longitudinal mixed-effect models were used to assess the effects of SNP genotype on FSH and LH levels over time via additive and recessive models. MAIN RESULTS AND THE ROLE OF CHANCE: An overall marked increase in serum FSH and LH following administration i.v. of 100 µg of an LHRH-analogue was found (P < 0.0001 for linear trend, both models). Peak levels of LH were significantly higher in TT carriers than in GT and GG carriers (P = 0.012); no significant between-groups difference was found concerning stimulated FSH levels. In both the additive and recessive model, the main effect of T allele(s) did not reach statistical significance concerning FSH levels (P = 0.9502 and P = 0.8576, respectively), yet interaction effects over time demonstrated an attenuated response in T-allele carriers compared to the GG-allele carriers (P = 0.0219 and P = 0.0276). Main and interaction effects for LH were significant in both the additive (P = 0.0022 and P = 0.0013, respectively) and recessive model (P = 0.0025 and P = 0.0016, respectively). LIMITATIONS, REASONS FOR CAUTION: Given the retrospective nature of the study and the small number of TT carriers, results should be interpreted with caution. WIDER IMPLICATIONS OF THE FINDINGS: The FSHB c.-211G>T polymorphism might result in an impaired response to endogenous, as well as exogenous, GnRH stimulation. This finding might contribute to the clinical phenotype of reduced testicular volume and sperm count for patients carrying one or two T alleles. STUDY FUNDING/COMPETING INTEREST(S): Parts of the study were supported by the German Research Foundation (CRU326 Male Germ Cells). On behalf of all authors, the corresponding author states that there is no conflict of interest. TRIAL REGISTRATION NUMBER: NA.

Defects in the cytoplasmic assembly of axonemal dynein arms cause morphological abnormalities and dysmotility in sperm cells leading to male infertility.

Axonemal protein complexes, such as outer (ODA) and inner (IDA) dynein arms, are responsible for the generation and regulation of flagellar and ciliary beating. Studies in various ciliated model organisms have shown that axonemal dynein arms are first assembled in the cell cytoplasm and then delivered into axonemes during ciliogenesis. In humans, mutations in genes encoding for factors involved in this process cause structural and functional defects of motile cilia in various organs such as the airways and result in the hereditary disorder primary ciliary dyskinesia (PCD). Despite extensive knowledge about the cytoplasmic assembly of axonemal dynein arms in respiratory cilia, this process is still poorly understood in sperm flagella. To better define its clinical relevance on sperm structure and function, and thus male fertility, further investigations are required. Here we report the fertility status in different axonemal dynein preassembly mutant males (DNAAF2/ KTU, DNAAF4/ DYX1C1, DNAAF6/ PIH1D3, DNAAF7/ZMYND10, CFAP300/C11orf70 and LRRC6). Besides andrological examinations, we functionally and structurally analyzed sperm flagella of affected individuals by high-speed video- and transmission electron microscopy as well as systematically compared the composition of dynein arms in sperm flagella and respiratory cilia by immunofluorescence microscopy. Furthermore, we analyzed the flagellar length in dynein preassembly mutant sperm. We found that the process of axonemal dynein preassembly is also critical in sperm, by identifying defects of ODAs and IDAs in dysmotile sperm of these individuals. Interestingly, these mutant sperm consistently show a complete loss of ODAs, while some respiratory cilia from the same individual can retain ODAs in the proximal ciliary compartment. This agrees with reports of solely one distinct ODA type in sperm, compared to two different ODA types in proximal and distal respiratory ciliary axonemes. Consistent with observations in model organisms, we also determined a significant reduction of sperm flagellar length in these individuals. These findings are relevant to subsequent studies on the function and composition of sperm flagella in PCD patients and non-syndromic infertile males. Our study contributes to a better understanding of the fertility status in PCD-affected males and should help guide genetic and andrological counselling for affected males and their families.

A germ cell-specific ageing pattern in otherwise healthy men.

Life-long sperm production leads to the assumption that male fecundity remains unchanged throughout life. However, recently it was shown that paternal age has profound consequences for male fertility and offspring health. Paternal age effects are caused by an accumulation of germ cell mutations over time, causing severe congenital diseases. Apart from these well-described cases, molecular patterns of ageing in germ cells and their impact on DNA integrity have not been studied in detail. In this study, we aimed to assess the effects of 'pure' ageing on male reproductive health and germ cell quality. We assembled a cohort of 198 healthy men (18-84 years) for which end points such as semen and hormone profiles, sexual health and well-being, and sperm DNA parameters were evaluated. Sperm production and hormonal profiles were maintained at physiological levels over a period of six decades. In contrast, we identified a germ cell-specific ageing pattern characterized by a steady increase of telomere length in sperm and a sharp increase in sperm DNA instability, particularly after the sixth decade. Importantly, we found sperm DNA methylation changes in 236 regions, mostly nearby genes associated with neuronal development. By in silico analysis, we found that 10 of these regions are located in loci which can potentially escape the first wave of genome-wide demethylation after fertilization. In conclusion, human male germ cells present a unique germline-specific ageing process, which likely results in diminished fecundity in elderly men and poorer health prognosis for their offspring.

The Ca2+ channel CatSper is not activated by cAMP/PKA signaling but directly affected by chemicals used to probe the action of cAMP and PKA.

The sperm-specific Ca2+ channel CatSper (cation channel of sperm) controls the influx of Ca2+ into the flagellum and, thereby, the swimming behavior of sperm. A hallmark of human CatSper is its polymodal activation by membrane voltage, intracellular pH, and oviductal hormones. Whether CatSper is also activated by signaling pathways involving an increase of cAMP and ensuing activation of PKA is, however, a matter of controversy. To shed light on this question, we used kinetic ion-sensitive fluorometry, patch-clamp recordings, and optochemistry to study transmembrane Ca2+ flux and membrane currents in human sperm from healthy donors and from patients that lack functional CatSper channels. We found that human CatSper is neither activated by intracellular cAMP directly nor indirectly by the cAMP/PKA-signaling pathway. Instead, we show that nonphysiological concentrations of cAMP and membrane-permeable cAMP analogs used to mimic the action of intracellular cAMP activate human CatSper from the outside via a hitherto-unknown extracellular binding site. Finally, we demonstrate that the effects of common PKA inhibitors on human CatSper rest predominantly, if not exclusively, on off-target drug actions on CatSper itself rather than on inhibition of PKA. We conclude that the concept of an intracellular cAMP/PKA-activation of CatSper is primarily based on unspecific effects of chemical probes used to interfere with cAMP signaling. Altogether, our findings solve several controversial issues and reveal a novel ligand-binding site controlling the activity of CatSper, which has important bearings on future studies of cAMP and Ca2+ signaling in sperm.

Rotational motion and rheotaxis of human sperm do not require functional CatSper channels and transmembrane Ca2+ signaling.

Navigation of sperm in fluid flow, called rheotaxis, provides long-range guidance in the mammalian oviduct. The rotation of sperm around their longitudinal axis (rolling) promotes rheotaxis. Whether sperm rolling and rheotaxis require calcium (Ca2+ ) influx via the sperm-specific Ca2+ channel CatSper, or rather represent passive biomechanical and hydrodynamic processes, has remained controversial. Here, we study the swimming behavior of sperm from healthy donors and from infertile patients that lack functional CatSper channels, using dark-field microscopy, optical tweezers, and microfluidics. We demonstrate that rolling and rheotaxis persist in CatSper-deficient human sperm. Furthermore, human sperm undergo rolling and rheotaxis even when Ca2+ influx is prevented. Finally, we show that rolling and rheotaxis also persist in mouse sperm deficient in both CatSper and flagellar Ca2+ -signaling domains. Our results strongly support the concept that passive biomechanical and hydrodynamic processes enable sperm rolling and rheotaxis, rather than calcium signaling mediated by CatSper or other mechanisms controlling transmembrane Ca2+ flux.