Reproductive Endocrinology · Ovarian Hormones
Ferlin A, Arredi B, Zuccarello D, Garolla A, Selice R, Foresta C
Insulin-like factor 3 (INSL3) is expressed in Leydig cells of the testis and theca cells of the ovary. This peptide affects testicular descent by acting on gubernaculum via its specific receptor leucine-rich repeat-containing G protein-coupled receptor 8 (LGR8). From initial animal data showing the cryptorchid phenotype of Insl3/Lgr8 mutants, an extensive search for mutations in INSL3 and LGR8 genes was undertaken in human patients with cryptorchidism, and a frequency of mutation of 4-5% has been detected. However, definitive proofs of a causative role for some of these mutations are still lacking. More recent data suggest additional paracrine (in the testis and ovary) and endocrine actions of INSL3 in adults. INSL3 circulates at high concentrations in serum of adult males and its production is dependent on the differentiation effect of LH. Therefore, INSL3 is increasingly used as a specific marker of Leydig cell differentiation and function.
Mazzilli R et al., 2026 · Journal of endocrinological investigation
Male factor could contribute, alone or in combination with female factor, to the inability to conceive in a couple in more than half of cases. The effect of male factor infertility (MFI) on embryological assisted reproductive technology (ART) outcomes remains an ongoing discussion. to evaluate the impact of MFI on embryo aneuploidy rates, to better understand the role and possible indication for Preimplantation genetic testing for aneuploidies (PGT-A), considering the role of sperm characteristics, paternal age, sperm DNA fragmentation and sperm aneuploidies. this narrative review included all available articles, published up to January 2026. Available evidence, often based on heterogeneous and old-fashioned methodologies, suggests that MFI may impair embryonic development, particularly in terms of fertilization rate and blastulation rate, more than embryo euploidy; however, a comprehensive evaluation of MFI should be integrated into clinical practice in the context of couple infertility, to also optimize the efficiency and outcomes of ART. Promising results emerged from sperm DNA fragmentation as a tool to predict embryo euploidy, but further investigations involving larger sample sizes and improved standardization are required.
Grande G et al., 2026 · The Journal of clinical endocrinology and metabolism · Free to read
Male factor infertility (MFI) is frequently labelled idiopathic when evaluation relies primarily on semen analysis, potentially overlooking endocrine and pathophysiological mechanisms relevant for targeted management. To phenotypically define MFI and develop a pathophysiology-based classification aimed at reducing idiopathic infertility following comprehensive evaluation. Prospective monocentric cohort study conducted at a tertiary referral academic centre. Eight hundred male partners of infertile couples evaluated between October 2024 and January 2026 after exclusion of isolated female factor infertility. Prevalence of MFI categories, hormonal patterns across phenotypes, and proportion of idiopathic infertility after comprehensive work-up. All patients underwent standardized clinical evaluation, hormonal assessment (total testosterone, FSH, LH), testicular ultrasound, and complete semen analysis. Microbiological testing, transrectal ultrasound, and genetic analyses were performed according to guidelines. Primary spermatogenic failure was the most prevalent category (56.0%), followed by infection/inflammation (22.4%) and hypogonadotropic hypogonadism (8.5%). Idiopathic infertility was identified in only 5.3% of cases. Distinct endocrine profiles were observed, with high-FSH spermatogenic failure representing the dominant phenotype. Comprehensive phenotyping markedly reduces the proportion of patients classified as having idiopathic infertility and identifies clinically relevant subgroups. This prospective study provides validation of a pathophysiology-based classification and supports a shift toward endocrine-integrated diagnostic strategies in male infertility, with potential implications for targeted management.
Ponce MR et al., 2026 · Andrology · Free full text on PubMed Central
Transgender individuals assigned male at birth (AMAB) may choose to preserve their fertility prior to starting gender-affirming hormone therapy (GAHT). However, limited data exist regarding the baseline reproductive and hormonal characteristics of this population before and after GAHT. To characterize semen quality and hormonal profiles in transgender AMAB individuals prior to GAHT and compare findings with cisgender men and with transgender individuals who discontinued GAHT for at least 3 months. This retrospective study included transgender AMAB individuals from two tertiary andrology centers who underwent sperm cryopreservation before GAHT initiation (treatment-naïve group). Clinical evaluation included anthropometric measures, testicular volume assessment, varicocele detection, and sex hormone measures. Semen parameters were analyzed according to WHO criteria and compared with those of cisgender men and previously treated transgender individuals. Thirty-two treatment-naïve transgender AMAB individuals were included. Hormonal parameters were generally within reference ranges. Only 46.9% of treatment-naïve individuals met WHO criteria for normozoospermia, compared with 75.5% of cisgender controls. Compared with nine previously treated individuals, estradiol levels were higher and seminal volume lower. A higher frequency of seminal abnormalities was observed, although not statistically significant. A substantial proportion of treatment-naïve transgender AMAB individuals exhibited impaired semen parameters prior to GAHT initiation. Prior GAHT exposure showed a trend toward poorer semen quality. These findings support early fertility counseling and preservation in transgender individuals prior to GAHT initiation.
Graziani A et al., 2026 · Andrology · Free to read
Besides gonadal involvement (hypogonadism, male factor infertility, and testicular hypotrophy), patients with Klinefelter syndrome (KS) may suffer from several extra-gonadic complications, including neoplastic events. The aim of this review is to summarize all major clinical evidence dealing with the association between KS and neoplastic diseases and provide practical suggestions for the management of patients with KS regarding neoplastic risk. This narrative review was conducted through a comprehensive search of the PubMed database, using combinations of the following keywords: "Klinefelter syndrome," "cancer," "neoplasm," "breast cancer," "germ cell tumor," "lymphoma," and "testosterone replacement therapy". KS is associated with a higher risk of breast cancer and mediastinal germ cell tumors and an apparent higher risk of hematological malignancies, in particular non-Hodgkin lymphoma and leukemia. Evidence on testicular cancer is limited, with no clear increase in risk attributable to KS, while prostate cancer has a lower risk and lower mortality rate. Given the complexity of the syndrome and the limited available evidence, regular clinical follow-up with targeted investigations when clinically indicated may facilitate early diagnosis and management of associated comorbidities.
Ferlin A et al., 2005 · Annals of the New York Academy of Sciences
Insulin-like factor 3 (INSL3) affects testicular descent. Mutations in the INSL3 gene or its receptor, LGR8/GREAT, can cause cryptorchidism. Expression of LGR8/GREAT in different tissues and production of INSL3 by adult-type Leydig cells suggest additional roles for this hormonal system in adults. We used a novel radioimmunoassay kit to measure INSL3 concentrations in the serum of normal men and those with different testicular pathologies. We demonstrate that INSL3 circulates in adult men and is almost exclusively of testicular origin. Subjects with severe testicular damage (infertility) produce small amounts of INSL3, and concentrations of this hormone seem to reflect the functional status of the Leydig cells. Analysis of men treated with different combinations of hormones of the hypothalamus-pituitary-testis axis suggests that the production of INSL3 is related to the luteinizing hormone.
Foresta C et al., 2004 · Reproductive biomedicine online
Cryptorchidism is the most frequent congenital anomaly of the urogenital tract in human males. INSL3 and LGR8/GREAT proteins seem to act as ligand and receptor respectively, and to have a role in gubernaculum development involved in testicular descent. Mutations in the INSL3 gene or LGR8/GREAT were found to be associated with cryptorchidism in humans. In a cohort of 135 ex-cryptorchid patients and 100 controls, mutations were sought in INSL3 and LGR8/GREAT genes by sequencing. Six patients were found with mutations in the INSL3 gene and four patients with LGR8/GREAT mutation (10/135, 7.4%). The 10 patients show different phenotypes, ranging from normozoospermia to complete azoospermia, and from bilateral cryptorchidism to retractile testes. Furthermore, the endocrine function of the testis appeared normal in all subjects. These findings demonstrate that INSL3-LGR8/GREAT mutations are frequently associated with human cryptorchidism, and that the only clinical consequence of alterations of the INSL3-LGR8/GREAT system seems to be failure of the testis to descend normally in the scrotum during embryonic development, without affecting the spermatogenic and endocrine components of the testis itself. The first analysis in humans of INSL3 was then performed using a novel radioimmunoassay kit to measure INSL3 concentrations in serum of adults. The results show that INSL3 circulates in adult men, it is a male-specific hormone, and it is of almost exclusively testicular origin. The role of this hormonal system in adulthood is, however, to date unknown.
Foresta C et al., 2004 · The Journal of clinical endocrinology and metabolism
Insulin-like factor 3 (INSL3) is a member of the relaxin-insulin family, and it is expressed in pre- and postnatal Leydig cells of the testis. This peptide affects testicular descent during embryonic development, and mutations in INSL3 gene or its receptor LGR8 (leucine-rich repeat-containing G protein-coupled receptor 8)/GREAT (G protein-coupled receptor affecting testicular descent) cause cryptorchidism in humans. The expression of LGR8/GREAT in different tissues and the production of INSL3 also by adult-type Leydig cells suggest additional roles of this hormonal system in adulthood. In this preliminary report we performed the first analysis in humans of INSL3 using a novel RIA kit to measure INSL3 concentrations in serum of normal men and with different testicular pathologies. The results show that INSL3 is circulating in adult men, and it is almost exclusively of testicular origin. Subjects with severe testicular damage, such as men with severe infertility, produce low amount of INSL3, and the concentrations of this hormone seem to reflect the functional status of the Leydig cells. In particular, INSL3 concentrations may be an even more sensitive marker of Leydig cell function than testosterone itself. Analysis of men treated with different combinations of hormones of the hypothalamus-pituitary-testis axis suggests that the production of INSL3 is related to LH in a manner similar to that of the LH-testosterone axis.
Facondo P et al., 2020 · Protein and peptide letters
This article reviews the role of INSL3 as biomarker of Leydig cell function and its systemic action in testis-bone-skeletal muscle crosstalk in adult men. Insulin-like factor 3 (INSL3) is a peptide hormone secreted constitutively in a differentiation-dependent mode by testicular Leydig cells. Besides the role for the testicular descent, this hormone has endocrine anabolic functions on the bone-skeletal muscle unit. INSL3 levels are low in many conditions of undifferentiated or altered Leydig cell status, however the potential clinical utility of INSL3 measurement is not yet well defined. INSL3 levels are modulated by the long-term cytotropic effect of the hypothalamicpituitary- gonadal axis, unlike testosterone that is acutely sensitive to the stimulus by luteinizing hormone (LH). INSL3 directly depends on the number and differentiation state of Leydig cells and therefore it represents the ideal marker of Leydig cell function. This hormone is more sensitive than testosterone to Leydig cell impairment, and the reduction of INSL3 in adult men can precociously detect an endocrine testicular dysfunction. Low INSL3 levels could cause or contribute to some symptoms and signs of male hypogonadism, above all sarcopenia and osteoporosis. The measurement provided suggested that the measurement of INSL3 levels should be considered in the clinical management of male hypogonadism and in the evaluation of testicular endocrine function. The monitoring of INSL3 levels could allow an early detection of Leydig cell damage, even when testosterone levels are still in the normal range.
