Thyroid Tests Overlooked in Fertility cases

Undiagnosed, misdiagnosed and untreated thyroid disease can be a major factor in infertility cases. Many of my patients walking in the door are either being treated for hypothyroidism with synthroid or their thyroid panel is labelled as “normal.”

Thyroid function can affect fertility in many ways resulting in luteal phase defect, anovulatory cycles (lack of ovulation), irregular menstrual cycles, high prolactin levels, recurrent miscarriage, and sex hormone imbalances. Not only is proper thyroid function required for conception, it is necessary for a healthy pregnancy and birth.

TSH (thyroid stimulating hormone) is the routine test done in any infertility work-up. Is this the full story? It never is.

Comprehensive thyroid testing should consist of 3 other tests to ensure any thyroid illness is ruled in or out in your infertility case. Especially in cases where patients are on synthroid, comprehensive testing can unveil underlying causes of TSH fluctuations and determine if synthroid is the best fit.

Comprehensive testing includes:

TSH

T3

T4

Thyroid autoimmune testing such as thyroid stimulating hormone (TSI), thyroid peroxidase (TPO), and thyroglobulin antibodies

Both T3 and T4 can provide insight into the production of your thyroid hormones. For example, low T4 and normal TSH is a common clinical picture I see. Specific treatment targeting low T4 can improve thyroid function and increase production of T3 (the active thyroid hormone).

Autoimmune thyroid testing is another common test that is often overlooked. A good handful of patients I see that frequently have normal TSH, T4, and T3, have elevated thyroid antibodies.

An article from the Nature Clinical Practice of Endocrinology and Metabolism, states: “the presence of thyroid autoimmunity is associated with a significantly raised frequency of miscarriages, even when thyroid function is apparently normal.”

Reference ranges should also be looked at during a proper thyroid evaluation. For example, the reference range for TSH is 0.20-4.00 mU/L. For optimal fertility, TSH should be less than 2.5 mU/L.

Thyroid disorder is a condition which is co-morbid with several others therefore your infertility investigation should not end there. Thyroid antibodies are commonly raised in infertile women with endometrosis and polycystic ovarian syndrome (PCOS). Further testing should be done to rule out other possible co-morbidities.

The term “normal” is something I hear frequently in our fertility visits and in a good number of couples, proper investigation and thorough testing was never done, leaving their case as either “unexplained” infertility or that their only option is IVF or IUI.

If you are struggling with infertility, recurrent miscarriage, symptoms of hypothyroidism, been on synthroid for a number of years with no change in your health, proper testing may be warranted and required to optimize your thyroid function for a healthy conception and birth.

In good health,

Dr. Kirti Deol