What role does FT4 play in fertility?

FT4 (free thyroxine) is a key thyroid hormone and plays a significant role in fertility. Balanced FT4 levels are essential for regulating the menstrual cycle, ovulation, and early pregnancy maintenance. Both hypothyroidism (low FT4) and hyperthyroidism (high FT4) can impair fertility by disrupting the hypothalamic-pituitary-ovarian axis. The evidence is strong, based on clinical studies and endocrine guidelines. However, a single FT4 value from a home test does not replace medical diagnosis; interpretation requires context including TSH, T3, and clinical symptoms. Direct-to-consumer DNA tests cannot reliably predict FT4 levels; thyroid function is measured via blood biomarkers, not genetics alone. Caveat: If you have fertility concerns and abnormal thyroid values, consult an endocrinologist for proper evaluation and treatment.