Elevated Miscarriage Risk and Lower Egg Reserve connected to Suboptimal Thyroid Function
Lately over the last few years we have seen more research suggesting that what may be considered normal thyroid function for the general population is much wider than the range considered optimal for Patients dealing with infertility. In fact, many Patients are told that their thyroid hormone levels are normal, even though by the new standards suggested in the research the thyroid may be under functioning for optimal reproductive outcomes.
One thing about the thyroid gland is that its activity affects various organs and activity. In addition to ovulatory function, follicle maturation, and reproductive hormone production it also has an affect on mood, metabolic health, sleep quality, digestive health cardiovascular health and much more.
Elevated Miscarriage Risk, Lower Live Birth Rates, and Lower Embryo Implantation Rates:
A new systematic review and meta-analysis looking at over 20 clinical trials found that Patients who tested positive for thyroid auto-immunity (TAI) were at a 52% increased risk of miscarriage, 28% reduced likelihood of embryo implantation and 27% less likely to have a live birth when compared to patients that tested negative for TAI. Earlier research had suggested that the presence of thyroid antibodies, independent of the levels of thyroid hormone produced, could damage eggs and affect reproductive outcomes.
What are thyroid antibodies?
There are two types of thyroid antibodies that can be screened for: anti-thyroid peroxidase antibody (Anti-TPO AB) and anti-thyroglobulin antibody (Anti-TG AB). Anti-TPO antibodies attack an important enzyme in the thyroid used to produce thyroid hormones and the Anti-TG antibodies attack the a protein inside of the thyroid called thyroglobulin.
How is Thyroid Autoimmunity Diagnosed?
A simple blood test can be done to help screen for these antibodies to help determine if a Patient has thyroid autoimmunity.
Who is at increased risk of thyroid autoimmunity?
Patients with first-degree relatives with thyroid disorders and those that are currently pregnant are at an increased risk of thyroid autoimmunity. Patients in their postpartum phase may also be at an elevated risk of thyroid autoimmunity. This may be related to the fluctuation of sex hormones and changes in the immune system that occur during pregnancy and in the postpartum period.
Diminished Ovarian Reserve and Lower Egg Reserve Markers with high-normal TSH levels:
Thyroid stimulating hormone (TSH) is produced from the pituitary gland in the brain and signals the thyroid gland to produce more thyroid hormones. TSH is often checked as a marker for thyroid function because if the thyroid is under-functioning, the TSH levels rise in an attempt to send a stronger signal to the thyroid to work harder.
Normally TSH should be within a specific range for the general population: 0.5 - 5.0 mIU/L
The newly published research supports previous articles that found that a TSH above 2.5 mIU/L (but still below 5.0 mIU/L) may negatively affect reproductive outcomes in Patients dealing with infertility. The study included 3501 Patients and they observed that those with a TSH above 2.5 (but still below 5) had a higher risk of being diagnosed with diminished ovarian reserve (DOR). They were observed to have lower anti-mullerian hormone (AMH) levels as well as lower follicle counts on an ultrasound. However, this research paper was an observational study so it can only establish correlation and not causation between high-normal TSH levels and risk of DOR.
Treatments for Thyroid-Autoimmunity and Elevated TSH:
This will depend on a case-by-case basis for each Patient. A proper evaluation is needed to help determine if thyroid hormone replacement therapy should be considered and to have an in-depth conversation regarding additional risk factors that may impact thyroid function.
This article is being shared as educational content and is in no way a replacement for medical advice or medical care, it is advised that anyone concerned about their Health should speak with their Naturopathic Doctor. Please discuss with your healtcare provider and only make changes to your medications regimen if recommended by your doctor and under their guidance and supervision.
Li, N., Lu, Y., Si, P., Li, Z., Qin, Y., & Jiao, X. (2022). The impact of moderately high preconception thyrotropin levels on ovarian reserve among euthyroid infertile women undergoing assisted reproductive technology. Thyroid, 32(7), 841–848.
Busnelli, A., Beltratti, C., Cirillo, F., Bulfoni, A., Lania, A., & Levi-Setti, P. E. (2022). Impact of thyroid autoimmunity on assisted reproductive technology outcomes and Ovarian Reserve Markers: An updated systematic review and meta-analysis. Thyroid.