TSH Test: What Your Thyroid Stimulating Hormone Means

TSH stands for thyroid stimulating hormone. It is made by the pituitary gland in your brain and tells your thyroid how much hormone to produce. When thyroid hormone is low, TSH rises. When thyroid hormone is high, TSH drops.

TSH is usually the first test doctors order because it is sensitive. If TSH is abnormal, free T4 and sometimes free T3 are checked to see how the thyroid is actually performing.

Thyroid hormone regulates metabolism, energy, body temperature, mood, heart rate, digestion, and menstrual cycles. An underactive thyroid can cause fatigue, weight gain, cold intolerance, constipation, and low mood. An overactive thyroid can cause anxiety, weight loss, heat intolerance, and rapid heartbeat.

Women are several times more likely than men to develop thyroid conditions, and pregnancy and postpartum can significantly affect TSH.

TSH is not something you get from food. It is a hormone your body makes. Iodine, however, is essential for thyroid hormone production. Iodine is found in iodized salt, seafood, dairy, and eggs. Both too little and too much iodine can affect thyroid function.

Age, sex, pregnancy, postpartum changes, autoimmune disease, iodine intake, medications such as lithium or amiodarone, and pituitary issues can all affect TSH. High or low TSH should be interpreted alongside free T4 and symptoms.