Thyroid stimulating hormone (TSH) and infertility: the effect of TSH on embryo quality and IVF outcomes

Abstract

OBJECTIVE: Currently accepted normal values for TSH have been questioned. Patients with TSH values in the high end of the normal range (2.5 to 5.0 IU/L) appear to be at increased risk for development of hypothyroidism compared to patients with TSH values in the low end of that range (0.5 to <2.5 IU/L). Some experts have recommended treatment for such patients who may be at risk for adverse effects of hypothyroidism, including patients attempting to conceive, but this remains controversial. This study examines the relationship between TSH values, embryo quality, and IVF outcome. DESIGN: A retrospective study of 622 first IVF cycles from 1999 to 2003 at a private infertility clinic. MATERIALS AND METHODS: Patients with TSH values of 0.5 to 5.0 IU/L were included and divided into two groups: Group A) TSH 0.5 to <2.5 IU/L, and Group B) TSH 2.5 to 5.0 IU/L. Patients using donated oocytes, with endocrine disorders, and severe endometriosis were excluded. The student's t-test, and the chi-square test were used for statistical analyses. RESULTS: There were no significant differences between Groups A and B with respect to patient age, number of oocytes retrieved, cell number on day 3, fragmentation on day 3, number of day 3 high quality embryos, number of embryos replaced per transfer, embryos frozen, fertilization rate, implantation rate, spontaneous abortion rate, or live birth rate. The percent of day 3 embryos with multinucleated (23.7 vs 21.4, p = 0.019), uneven (36.4 vs 32.8, p = 0.001), and disorganized (21.8 vs 20.4, p = 0.042) blastomeres appeared to be significantly higher in Group B than Group A. CONCLUSIONS: The possibility that some patients with normal TSH levels may have subclinical hypothyroidism is of significant concern in the context of infertility treatment. While our study suggests that overall quality of the embryo cohort in patients with low normal TSH levels may be better than those in patients with high normal TSH levels, this difference is not reflected in the implantation or live birth rate. Therefore it remains to be seen in larger studies whether treatment of IVF patients with high normal TSH levels is clinically justified.