Thyroid hormones play a crucial role in regulating the menstrual cycle. Both hypothyroidism and hyperthyroidism can cause menstrual irregularities. Hypothyroidism often leads to menorrhagia (heavy menstrual bleeding) or oligomenorrhea (infrequent menstrual periods), whereas hyperthyroidism can cause amenorrhea (absence of menstruation) or polymenorrhea (frequent menstrual periods).
