Can thyroid issues affect periods?

Yes — thyroid dysfunction is among the most common and most easily missed causes of menstrual irregularity. An underactive thyroid typically causes heavier or more frequent bleeding, though it can also lengthen cycles or stop them. An overactive thyroid tends to cause lighter, less frequent periods. The link runs through the hypothalamic-pituitary axis that governs your cycle, and hypothyroidism also raises prolactin, which independently suppresses ovulation. The encouraging part is that correcting thyroid function usually restores normal cycles, often within a few months, without any treatment aimed at the periods themselves. A TSH test is inexpensive and widely available. If it is abnormal, free T4 and thyroid antibodies usually follow. Two practical points. Ask for prolactin to be checked at the same time, since the two travel together. And if you are trying to conceive or already pregnant, thyroid targets are tighter than the general population range — make sure whoever orders the test knows.