## How does TSH impact the activity of the thyroid? The thyroid-stimulating hormone ([TSH](https://ul.orna.me/KOge/librarybiomarker?id=137)) is produced by the pituitary gland at the base of the brain. It stimulates the thyroid to produce more hormones when necessary. An increased level of TSH can be a sign of underactive thyroid. Research has shown that women who have unexplained [infertility](https://ul.orna.me/KOge/librarydisease?id=187) almost twice as often have a higher level of thyroid-stimulating hormones than women who couldn't conceive because their partners had male factor infertility. ## The causes of unexplained infertility Unexplained infertility is diagnosed for those who cannot conceive after several months of attempts in the absence of other health issues preventing conception. According to the research by JCEM (the Journal of Clinical Endocrinology & Metabolism), unexplained infertility affects 10–30 % of infertile couples. The study's senior author, Pouneh K. Fazeli, M.D., M.P.H. of Massachusetts General Hospital and Harvard Medical School in Boston, Massachusetts, said, "When couples who are ready to start a family are unable to conceive despite extensive planning, multiple doctor's visits, and expensive treatments, it can be emotionally devastating. Since our study shows that women with unexplained infertility have higher TSH levels compared to women experiencing infertility due to a known cause, more research is needed to determine whether treating these higher TSH levels with thyroid hormone can improve their chances of getting pregnant." ## Available evidence During cross-sectional research, the scientists have analyzed data from patients aged 18–39 years old who were diagnosed as infertile during the period from 2000 until 2012. The study included only those women who had regular menstrual cycles and had normal fertility evaluations. The research has found that women with unidentified infertility had a considerably higher level of TSH hormone than those who could not conceive due to known cause. According to Fazeli, the results of this research create new opportunities for treating infertility in women.