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 referred to as the “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. Some such effects of thyroid disorders may include hair loss and joint pain; hair loss could mean that your thyroid is over- or under-producing its related hormones, while joint pain may be linked to the underproduction of T3 and T4.
A gland in our brain known as the pituitary is ultimately in charge of how much T3 and T4 is made and distributed by the thyroid. It does so using thyroid stimulating hormone (TSH). If functioning properly, the pituitary should produce and secrete TSH if levels of T3 and T4 in the body are low, in turn causing the thyroid to make and distribute these key hormones; the pituitary should secrete less TSH if there’s already a healthy amount of T3 and T4 circulating in your body.