Thyroid Function and Fertility — Why TSH Alone Isn’t Enough

Thyroid function is one of the most overlooked factors in fertility assessment — and one of the most impactful. Yet a standard GP panel typically checks TSH alone, which frequently misses the full picture.

A narrative review published in the Journal of Endocrinological Investigation examined the impact of impaired thyroid function on both female and male fertility, covering spontaneous conception through to assisted reproductive technology outcomes.

The thyroid plays a direct role in regulating the hormonal environment required for ovulation, implantation and healthy early pregnancy. Even subclinical thyroid dysfunction — where TSH sits within the standard reference range but Free T3, Free T4 or thyroid antibodies signal an underlying problem — can meaningfully affect fertility outcomes.

Thyroid autoimmunity in particular is associated with increased miscarriage risk and reduced IVF success rates, even when TSH appears normal. This is why a complete thyroid assessment — including Free T3, Free T4 and thyroid antibodies — is a foundational part of any preconception biomarker evaluation.

This is precisely why our Fertility Support Program goes beyond TSH. A complete picture of thyroid health is non-negotiable when you’re trying to optimise for conception.

Source: Mazzilli et al., Journal of Endocrinological Investigation, 2022.
Read the full review here