What role does FT3 play in fertility?

FT3 (free triiodothyronine) is the biologically active thyroid hormone and plays a critical role in female fertility. It regulates ovulation, follicle maturation, and endometrial receptivity. Optimal FT3 levels are essential for conception; even mild thyroid dysfunction (e.g., subclinical hypothyroidism) can disrupt menstrual cycles and impair implantation. Strong human evidence links hypothyroidism to increased miscarriage risk and reduced fertility. However, FT3 alone is not sufficient for assessment – TSH and fT4 are also key markers. For fertility concerns, a full thyroid panel (TSH, fT3, fT4, antibodies) should be evaluated by a physician. Caveat: Consumer home tests for FT3 are not diagnostic; results must be interpreted in clinical context. Lifestyle factors, iodine status, and autoimmune conditions also influence thyroid function and fertility.