The thyroid is an organ shaped akin to a butterfly located in our throats, close to the larynx and trachea. The thyroid’s main function is to produce and secrete hormones. This process hinges upon iodine, a substance that’s not only essential but also unique to thyroid hormones.
The two thyroid-produced hormones are called T3 and T4. They’re frequently called “metabolic hormones” because our basal metabolic rate–or how much energy we use when we’re resting–is influenced by how much T3 and T4 we have floating around our bodies. We also need sufficient levels of thyroid hormones in our bodies to make proteins, as well as to develop and grow tissues from when we’re developing fetuses through childhood. In fact, T3 and T4 are especially important in the nervous system’s healthy development, and continue to support its function in adulthood.
T3 and T4 have complex relationships with our reproductive hormones, too. Because of this, imbalances in them can affect our fertility, sex drive, and other reproductive behaviors. Furthermore, excessive levels of them speeds up our heart rate and blood pressure, and strengthens the heartbeat.
Thyroid disorders–which generally stem from dysregulated thyroid hormones–may have varied and sometimes even severe effects on the body due to the diverse functions of the T3 and T4 hormones.