Under high stress and elevated cortisol levels, the form of triiodothyronine that forms in circulation is reverse T3 (rT3), which is an inactive form.
Under high stress in conjunction with elevated cortisol levels, the form of triiodothyronine (T3) that is formed in circulation is reverse T3 (rT3). Cortisol can influence the conversion of thyroxine (T4) to its inactive form, rT3, rather than to the active form, T3. Under normal conditions, T3 is the more active thyroid hormone controlling the basal metabolic rate, but under stress, the body appears to conserve energy by converting T4 to the less active rT3. This is a regulatory mechanism to decrease metabolic activity during periods of prolonged stress.
The complete question is-
How does high stress, coupled with elevated cortisol levels, influence the form of triiodothyronine (T3) in circulation? Select the most appropriate option from the following: free T3 (FT3), reverse T3 (rT3), diiodothyronine (DIT), or thyroxine.