Thyroid Status and Sperm Abnormality Phenotypes Among Infertile Males Attending a Tertiary Referral Center in Bangladesh: A Cross-Sectional Study

Background Thyroid hormones triiodothyronine (T3) and thyroxine (T4) are recognized modulators of male reproductive physiology, acting on Sertoli cells, Leydig cells, and germ cells to regulate spermatogenesis. Despite growing evidence linking thyroid dysfunction to altered semen quality, the association between thyroid status and specific sperm abnormality phenotypes remains insufficiently characterized, with no prior data available from Bangladesh. This study aimed to evaluate thyroid status and its association with sperm abnormality phenotypes among infertile males attending a tertiary referral center in Bangladesh. Methods A hospital-based cross-sectional observational study was conducted at the Reproductive Endocrinology and Infertility outpatient department and In Vitro Fertilization (IVF) Center, Dhaka Medical College Hospital, Bangladesh, from January 2025 to June 2025. Ninety infertile males aged 21-50 years with confirmed abnormal semen parameters were enrolled using purposive sampling. Participants were classified into four phenotypic groups per WHO 2021 sixth edition criteria: oligospermia, isolated asthenozoospermia, oligo-asthenozoospermia, and astheno-teratozoospermia. Individuals with chronic systemic diseases independently associated with altered thyroid or reproductive function were excluded. Serum T3, T4, TSH, and follicle-stimulating hormone (FSH) were measured by chemiluminescence immunoassay (CLIA). Statistical analysis included the Kruskal-Wallis test, Mann-Whitney U test, chi-squared test, and Spearman rank correlation, using SPSS version 26 (IBM Inc., Armonk, New York). Results The median age was 35.0 years (IQR: 30.0-38.5). Oligospermia was the most prevalent phenotype (62.2%), followed by oligo-asthenozoospermia (22.2%) and isolated asthenozoospermia (12.2%). Hypothyroidism was disproportionately prevalent among men with oligo-asthenozoospermia (70.0%), while hyperthyroidism was more frequent among asthenozoospermic men (27.3%). Statistically significant differences in serum T3 (p=0.017), T4 (p=0.041), and TSH (p=0.003) were observed across phenotypic groups. Thyroid status was significantly associated with semen abnormality type (p<0.001). Serum T3 and T4 correlated positively with total sperm count (rs=0.427 and 0.422, respectively) and sperm morphology (rs=0.532 and 0.370), while TSH showed significant inverse correlations with both parameters. No significant correlation was observed with sperm motility. Conclusions Thyroid dysfunction, particularly hypothyroidism, was significantly associated with specific sperm abnormality phenotypes among infertile males in Bangladesh. Thyroid hormone levels correlated meaningfully with sperm count and morphology, suggesting that thyroid evaluation may be considered as part of the male infertility workup. Larger, multicenter, longitudinal studies are needed to confirm these associations and guide clinical practice.