Thyroid stimulating hormone (TSH): does it live up to its promises in the andrology laboratory?

Research on Thyroid function in fertility/infertility has mainly focused on women, while men have scarcely been investigated. We investigated the association between TSH pattern and semen parameters, considering age, BMI, smoking and alcohol drinking. For 2021-2023, we examined all 346 male patients (infertile/fertile) in a Center for Reproductive Medicine at Germany. Age, BMI, smoking and detailed alcohol intake were recorded. A blood sample was taken from each patient in connection with the sperm collection to measure TSH, FSH, LH, prolactin, testosterone levels and the LH to testosterone ratio. Spearman's correlation coefficients were used to determine correlations among hormones. Statistical analyses were performed using semen parameters as dichotomized using world health organization reference values.

The analysis explored relationships between age, BMI, smoking, alcohol consumption and semen parameters with TSH levels. The mean age and BMI were 35.8 ± 7.43 years and 27.1 ± 4.54 kgm^- 2, respectively. Of all participants, 37% reported being smokers, alcohol consumption was 3% every day, 35% each week, 44% each month and 17% none. For TSH, we recorded 309 TSH levels, and the normal range was given as 0.4 to 4 mIU/L; 95% of the participants were in this category. Only a few participants were outside this range, with 1% below and 4% above. TSH levels were not found to be significantly affected by age, BMI, smoking, alcohol consumption or season. We found a positive correlation between TSH and prolactin (r = 0.199, p = 0.0001). Logistic regression showed that when TSH values were within the normal range, sperm counts were significantly higher (odds ratio:1.302, P = 0.043; confidence interval 95%:1.009-1.681).

Male patients with abnormal TSH levels are not very common in this region (5%). Further studies regarding thyroid tests in andrology laboratory are required. TSH assessment in infertile couples should be routine in both partners, given the recorded worldwide increase in thyroid dysfunction.