Serum prolactin and TSH in an in vitro fertilization population: Is there a link between fertilization and thyroid function?

Purpose: Measurements of TSH and prolactin are generally included in the evaluation of female infertility, but their value in women coming to in vitro fertilization (IVF) has been questioned. Methods: In this study, we sought to investigate whether prolactin or TSH, measured in 509 specimens collected prior to therapy, predicted outcome in a prospective study of couples undergoing IVF between 1994 and 2001. Results: TSH was higher in women whose fertility problem was attributed to a male factor, and prolactin was lower if the measurement was taken during menses. TSH and prolactin were positively correlated (p < 0.0001). Neither TSH nor prolactin levels correlated with overall IVF outcome; however, TSH levels were significantly higher among women who produced oocytes that failed to be fertilized and this finding persisted after adjustment for several covariates, including sperm motility. Among women who had a least one oocyte inseminated, the likelihood that they would have fewer than 50% of their eggs fertilized was significantly related to higher TSH levels in a multivariate model. Conclusion: We conclude that TSH may predict poor fertilization in IVF and reflect the importance of thyroid hormones in oocyte physiology.