Cortisol is a hormone produced by your adrenal glands. Your adrenal glands sit just on top of your kidneys. While cortisol is often thought of as a stress hormone, it actually plays a significant role in many aspects of your physiology. The secretion of cortisol is controlled by the hypothalamus, the pituitary gland, and the adrenal gland. This combination of glands is referred to as the HPA axis.
Most of the cells of the body have cortisol receptors, therefore cortisol can impact many functions in the body. Cortisol helps regulate blood sugar levels, metabolism, sleep and wake cycle, inflammation, memory, salt and water balance, blood pressure, and hormones.
So, what’s the connection with cortisol and hypothyroidism?
Cortisol impacts thyroid physiology in multiple ways. Elevated cortisol can reduce or suppress the Hypothalamic-Pituitary-Axis (HPA) reducing levels of TSH. Lowered TSH can reduce T4 and T3 production. Chronic elevations of cortisol can reduce the conversion of T4 to T3 and increase the conversion of T4 to rT3. Cortisol can raise Thyroid Binding Globulin resulting in reduced free thyroid hormone available to your cells.
Thyroid hormone also impacts cortisol production and metabolism. Both hypo and hyper thyroid states can result in increased or decreased cortisol production depending on the length of time in either state. In states of hypothyroidism you may experience reduced ability to metabolize cortisol leading to elevated levels of cortisol or its inactive form cortisone.