The effect of impaired thyroid-stimulating hormone (TSH) levels on fertilization rate of infertile women with endometriosis

The relationship between endometriosis and thyroid disorders and the subsequent impact on fertility outcomes is still controversial. The present study was performed with aim to evaluate the effect of impaired thyroid-stimulating hormone (TSH) levels on fertilization rate of infertile women with endometriosis.

In this secondary analysis of cohort data, 179 infertile women with endometriosis were selected as the case group and 200 women with diagnosis of tubal factor or unexplained infertility were selected as the control group. Two subgroups of TSH levels above 2.5 mlU/L (with or without levothyroxine use) and TSH levels less than 2.5 mlU/L with levothyroxine use as patients with thyroid dysfunction and women with TSH levels less than 2.5 mlU/L without use of Levothyroxine were considered as thyroid-healthy subjects. Antral follicle count and fertilization rate were compared between the two groups. Data analysis was done using SPSS statistical software (version 24) and ANOVA test. P<0.05 was considered significant.

The mean of TSH in women with endometriosis was significantly higher than the control group (P=0.02, Cohen d=0.77, 95% CI: 0.02-0.43). When women were classified based on the presence or absence of endometriosis and serum TSH levels above 2.5 mlU/L, serum levels of FSH (P=0.76), LH (P=0.91), and fertilization rate (P=0.51) did not significantly differ between the two groups.

It seems that thyroid disorders are more common in women with endometriosis. However, there was no significant effect on the results of assisted reproductive procedures related to the coexistence of endometriosis and higher TSH levels.