With normal thyroid function, when there is a need for more thyroid secretion, a signal is received by the pituitary gland which then releases a substance to stimulate thyroid function. As soon as the needed amount of thyroid secretion has then been released into the bloodstream, the pituitary gland gets the message, stops releasing its thyroid-stimulating substance, and less thyroid is produced. Through this sensitive “feedback” mechanism, the amount of thyroid hormone in the bloodstream is maintained in an effective, narrow range.

When thyroid function is deficient, the gland cannot respond adequately to the stimulus form the pituitary.  The “Barnes Basal Thyroid Temperature Test” is an excellent way to help you assess your thyroid function using basal body temperature (your body’s temperature at rest).  If the thyroid is low, the body’s temperature will drop below normal while the body is at rest or asleep.

Source: Barnes, B., & Galton, L. (1976). Hypothyroidism: The Unsuspected Illness. New York: Harper & Row.