Adding thyroid hormone to the in vitro fertilization (IVF) process produces more viable embryos and has the potential to increase the success rate of pregnancy, according to a ground-breaking U of G study.
A team of biomedical scientists discovered that adding the synthetic hormone to bovine eggs after fertilization boosted the number of viable embryos by 30 per cent.
They also found that the hormone-treated embryos were more advanced in morphology and cell number and had fewer damaged cells than the embryos developed without the hormone.
“These embryos were of higher quality, so there’s a greater chance they will survive and create a pregnancy,” says Prof. Allan King, who worked on the study with PhD student Fazl Ashkar. “Despite the widespread use of in vitro fertilization, only 25 to 30 per cent of the procedures result in a successful pregnancy, so any increase is beneficial.”
The thyroid hormone-treated embryos also showed a 25-per-cent increase in survival after freezing and thawing. Embryos are frozen for storage before they’re transferred to recipients.
Published in the journal Human Reproduction, the study involved bovine embryos because cows are one of the closest species to humans when it comes to reproduction.
“The cow is a good model for humans because both release one or two eggs per cycle and both have similar reproductive systems and thyroid hormone levels,” says Fazl. “Embryo development for humans and cows is also the same, with the gestation period being about nine months.”
The researchers turned their attention to thyroid hormone because women who have disturbances in fertility due to polycystic ovarian syndrome have levels of the hormone that are often lower than normal ranges.
“Thyroid hormone is involved in the regulation of gene expression, metabolism and growth, which are all areas important for early embryo development,” says Fazl.
For the first part of their research, they had to determine to what extent the hormone exists naturally in the female reproductive system.
This initial study, which was recently published in Experimental Biology and Medicine, revealed the hormone was present in all areas of the reproductive tract, including the oviduct, which is the primary site of fertilization.
“This told us that thyroid hormone should have a function in fertility,” says Fazl.
The next step was to investigate what impact adding the synthetic hormone to the in vitro process would have on early embryo development. The researchers added the hormone to the in vitro embryo production media at different stages of the process and found it had the most impact after the eggs were fertilized.
The scientists are now working with other research partners to explore the potential impact their findings can have on human IVF.
“Based on this research, it makes sense that thyroid hormone is important in embryo development regardless of the species,” says King. Because of the similarities in human and bovine reproduction, “we predict thyroid hormone will have an effect on pre-implantation and consequently post-implantation human embryo development. Thus we are hoping this research can help improve the efficiency of in vitro fertilization in humans.”