People whose bodies are not making enough thyroid hormone will feel tired, gain weight, be sensitive to cold and have dry skin, a poor memory and a slow heart beat.
Thyroid replacement should only be started after you have been tested for a lack of steroids. When this has been ruled out - or after steroid replacement therapy has been started, if tests show it is needed - then thyroid hormone replacement can be done.
Side Effects of Thyroid Hormone Replacement
Side effects only usually show up when you have been given too much thyroid hormone. The effects then include anxiety, a fast heart beat and tremor (a shakiness of the muscles that you cannot control).
If a person has blocked heart vessels and is given too much thyroid hormone, he or she may have chest pain or an abnormal heart rhythm. People who are at risk for heart conditions should be started on low doses of thyroid hormone. The dose should be increased slowly as needed.