Infertility can be a very challenging condition for women who want to become pregnant. They face the daunting task of going through a long list of potential causes, each needing to be evaluated and eliminated in order to identify the exact issue that needs to be resolved. The extensive process of elimination can involve lab tests, clinical examinations and uncomfortable invasive procedures. The distressful process can be emotionally and financially draining, and in about 10- 30% of the cases, no cause is even identified.

Doctors most commonly look for ovulation problems caused by health issues such as uterine fibroids, blocked fallopian tubes, or polycystic ovarian disease. Thyroid dysfunction is also recognized as a cause of infertility, but only when lab tests are out of normal range. If thyroid labs are within normal range, doctors may quickly move on to looking for other causes, overlooking the possibility that the lab tests may be missing more subtle thyroid imbalances.

Hopefully that practice will change in the future due to revelations made in recently published studies. Infertility research has indicated that it might be wise to investigate thyroid problems more closely and look for more subtle changes such as “subclinical” hypothyroidism when women have difficulty conceiving.

Subclinical hypothyroidism lacks a definitive definition, but it generally is considered to be an elevation of TSH (thyroid-stimulating hormone), despite normal thyroid hormone level. Elevated TSH is an indicator that thyroid hormone is low, and is a test that is typically used to diagnose hypothyroidism.

There is not consensus as to what constitutes elevated TSH, and whether that includes the upper limit within normal range. WebMD simply defines subclinical hypothyroidism as: 1) No symptoms or mild symptoms of hypothyroidism. Examples are fatigue, cold intolerance, consistent weight gain, depression, or memory problems. 2) Having a mildly high TSH and (3) Having a normal thyroxine (T4) level.

In a recent study, women with unexplained infertility were compared to women who had known causes for their infertility. All the women in both groups had TSH within normal range, with no previous history of hypothyroidism or hyperthyroidism. It was shown that the women in the unknown group had significantly higher levels of TSH (although still within normal) compared to women who were infertile for other known causes. This lead the researchers to believe that mild variations in TSH levels, as in the case of subclinical hypothyroidism, could possibly be a cause of infertility. One of the researchers said “Since we now know from our study that there is an association between TSH levels at the high end of the normal range and unexplained infertility, it is possible that a high-normal TSH level may negatively impact women who are trying to get pregnant”.

Another example of a study connecting subclinical hypothyroidism to issues related to pregnancy was published a few years ago. It concluded that women with subclinical hypothyroidism were at higher risk of miscarriage. (read the summary here )

In the medical community, the question still remains as to whether women with subclinical hypothyroidism should be treated with thyroid medication if they are having difficulty getting pregnant. So far, the American Thyroid Association has not made that recommendation.

When it comes to infertility and other thyroid related symptoms, Dr. Wilson believes that TSH testing can miss the mark, and shouldn’t be the only test to assess thyroid function. Body temperature can actually be a much better indicator of subtle thyroid imbalances and it is very accurate. Read more about why temperature may be a better indicator then TSH HERE. Dr. Wilson believes there have been hundreds of families over the last 20 years that conceived through the use of T3 therapy for Wilson’s Temperature Syndrome after previously struggling with infertility.

Consistently low body temperature is the hallmark for Wilson’s Temperature Syndrome. Testing is as easy as using a thermometer and tracking your temperature. You can learn more about how to accurately take your temperature HERE.

The Journal of Clinical Endocrinology & Metabolism
Source Reference: Jokar TO, et al “Higher TSH levels within the normal range are associated with unexplained infertility” JCEM 2017; DOI: 10.1210/jc.2017-02120.