A doctoral thesis brought out the impact of female sex hormones on infertility treatment and tumour development

In today’s infertility treatment clinics there are always patients who continuously fail to conceive despite of good quality embryos transferred. One of the causes of not achieving a pregnancy is that endometrium might be un-receptive for embryo attachment. Endometrium is receptive for embryo implantation in a very limited time-period (so-called ‘window of implantation’, usually lasting only for 2-4 days). The endometrium tissue of women in reproductive age undergoes substantial monthly changes under the control of female steroid hormones – estrogen and progesterone.

To examine how the female steroid hormones – estrogen and progesterone – affect gene expression in the uterus, Karin Rosenstein applied genome-wide analyses in her doctoral thesis. As a result of the study potential target genes of these hormones were identified. It was also found that the female steroid hormone modulator tamoxifen used for the treatment of certain type of breast cancer clearly modulates the endometrial gene expression profile. These findings indicate that the treatment of breast cancer with tamoxifen is accompanied by a significant rise in endometrial cancer risk.

The use of steroid hormones is also essential in preparing the endometrium for frozen embryo transfers in infertility treatment.
The doctoral thesis examined endometrial gene expression in infertile women with recurrent implantation failure. According to the study results, it is not recommended to use exogenous steroid hormones on these women for preparing the endometrium for frozen embryo transfers.

The study carried out in the doctoral thesis shows that, on the one hand, steroid hormones facilitate in vitro fertilization, but on the other hand, they play a crucial role in causing female infertility and developing hormone dependent tumours.

Supervisors of the doctoral thesis: Professor Andres Salumets (the University of Tartu), Professor Madis Metsis (Tallinn University) and Jaak Simm, PhD (KU Leuven).
Opponents: Professor John Aplin (the University of Manchester, Institute of Human Development, United Kingdom) and Senior Researcher Kersti Lilleväli (the University of Tartu, Estonia).

The doctoral thesis has been published in the digital collection of TUT library at http://digi.lib.ttu.ee/i/?5130