Measuring thyroid stimulating hormone (TSH) levels is a standard part of a fertility evaluation, as thyroid function can significantly impact the ability to conceive and maintain a healthy pregnancy.
What is TSH and Why is it Important?
TSH regulates the thyroid gland’s activity, which produces thyroid hormones (T3 and T4). These hormones control metabolism, energy levels, and some bodily functions, including reproductive processes. Abnormal TSH levels can disrupt the thyroid hormonal balance and lead to issues that affect fertility.
High TSH Levels (Hypothyroidism): Elevated TSH levels indicate low thyroid hormone production, which can interfere with ovulation, cause irregular menstrual cycles, and increase the risk of miscarriage. Symptoms like fatigue, weight gain, and cold intolerance may accompany hypothyroidism.
Low TSH Levels (Hyperthyroidism): Low TSH levels suggest excessive thyroid hormone production, which can also disrupt ovulation and menstrual cycles. Hyperthyroidism is often associated with symptoms like weight loss, heat intolerance, and anxiety.
How Thyroid Health Affects Fertility
Proper thyroid function is important to reproductive hormone regulation. Abnormal TSH levels can adversely impact ovulation, fertilization, and implantation. Thyroid dysfunction can also affect the health of the endometrial lining, reducing the chances of a successful pregnancy.
Additionally, thyroid imbalances can impact assisted reproductive technologies (ART) such as in vitro fertilization (IVF). For example, hypothyroidism may decrease the success rates of IVF due to poor embryo implantation and development.
Measuring TSH Levels in Fertility Treatment
Your doctor will likely include a TSH test to assess thyroid function during your fertility workup. Normal TSH levels typically range from 0.4 to 4.0 mIU/L. However, for those trying to conceive, many fertility specialists aim for a narrower target range of 1.0 to 2.5 mIU/L or 1.0 to 4.0 mIU/L, as studies show this range is associated with better fertility outcomes.
If your TSH levels are outside the optimal range, your fertility specialist may recommend treatments or refer you to an endocrinologist for further treatment. Treatments to bring TSH levels to normal range include hormone replacement therapy, medications, lifestyle adjustments, and diet changes.
