Thyroid hormones, including free T4, influence the menstrual cycle by interacting with reproductive hormones such as estrogen and progesterone. Both hypothyroidism (low free T4 levels) and hyperthyroidism (high free T4 levels) can lead to irregular periods, heavy menstrual bleeding, or even amenorrhea (absence of menstruation). Therefore, assessing free T4 levels can be essential in diagnosing and managing menstrual irregularities.
