Abstract
Study question: we aimed to investigate the relationship between the tyg index and both semen and hormonal characteristics in a cohort of primary infertile men. Summary answer: almost one in two primary infertile men presented with a triglycerides/glucose index (tyg) suggestive of insulin resistance (ir). overall, patients with tyg suggestive of ir showed worse clinical, hormonal, and semen parameters. What is already known: male factor infertility (MFI) is often associated with metabolic disorders such as diabetes mellitus and metabolic syndrome, where insulin resistance (IR) plays a relevant pathological role. Recently, TyG has been suggested as a user-friendly IR marker. Study Design: serum hormones and the sperm DNA fragmentation index (SDF) were measured in every patient. The semen analysis was based on 2010 WHO reference criteria. Glucose and insulin levels were measured for every man after a 12-h overnight fast, and the homeostatic model assessment index (HOMA-IR) was then calculated and categorized using a 2.6 threshold. Similarly, fasting glucose and triglycerides levels were measured and the TyG index was calculated and categorized using an 8.1 threshold. Descriptive statistics and logistic regression models tested the association between the TyG and semen and hormonal characteristics. Participants: complete demographic, clinical, and laboratory data from 726 consecutive white European primary infertile men were considered for this analysis. Main results and the role of chance: the median (IQR) age was 39 (35–43) years. A TyG and HOMA suggestive for IR was found in 339 (46.6%) and 154 (21.2%) men, respectively. During the Spearman’s test, the TyG index was highly correlated with HOMA-IR (rho = 0.46, p < 0.001). Compared to men with a normal TyG, men with TyG > 8.1 were older, had greater BMI and CCI scores, and lower total testosterone and sperm concentration, but higher DFI, and presented a greater proportion of NOA (all p < 0.01). The multivariable logistic regression analysis showed that men with TyG > 8.1 were at higher risk of SDF > 30 (OR 1.92 (CI: 1.2–2.9)) and NOA (OR 1.78 (CI: 1.1–2.8)). Wider implications of the findings: the Tyng index may act as a reliable marker of IR in the clinical work-up of primary infertile men in real-life settings.
Highlights
We applied a new marker of insulin resistance (IR), termed the TyG index, which emerged as a simple, inexpensive and user-friendly biomarker, obtained by calculating fasting serum glucose and triglyceride values [20]
The TyG index was independently associated with oligozoospermia, Idiopathic NOA (iNOA) and sperm DNA fragmentation index (SDF), after accounting for common clinical and hormonal variables, outlining the relevance of IR testing in infertile men
Despite being strongly correlated, we observed that only 28% of our patients had a concomitant pathological TyG index and HOMA scores. This last finding might suggest that the TyG index may still eventually overestimate the proportion of primary infertile men with IR as compared with HOMA; as a consequence, these results suggest that further studies are needed to identify the best cutoff of the TyG index, at least to identify infertile men with IR, and all consequent clinical features
Summary
It is estimated that approximately 15% of couples are unable to achieve a spontaneous pregnancy after 1 year of regular, unprotected sexual intercourse and are classified as infertile. Among the treatable causes of male infertility, semen infections, smoking habits, alcohol consumption, abnormal DNA methylation, bacterial and viral infections, and recreational substance use have been consistently associated with impaired sperm quality [4–7]. Metabolic disorders such as prediabetes, diabetes mellitus (DM), and metabolic syndrome (MetS) are commonly found in infertile men [8–10]. In this context, DM and insulin resistance (IR) have been observed to negatively affect sperm quality and hormonal values, contributing to MFI [11]. The precise evaluation of IR appears to be of clinical relevance in the diagnostic work-up of infertile men
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