Thyroid hormone production is part of a negative feedback loop. A negative feedback loop is a mechanism within the body that helps to keep the body systems within balance or equilibrium. When the thyroid hormone is low the TSH or Thyroid stimulating hormone signals the body to produce the hormone to increase the bodies level. The body continues to produce more thyroid hormone until it balances the bodies' need. If all is working correctly when the Thyroid hormone level reaches the body ideal level the TSH level stabilizes as well and additional hormone production will not be stimulated. The correct level will be maintained.