Thyroid Hormone Therapy

Symptoms of hypothroidism (low levels of thyroid hormone) include fatigue, cold and heat intolerance, hypotension, fluid retention, dry skin and/or hair, constipation, headaches, low sexual desire, infertility, irregular menstrual periods, aching muscles and joints, depression, anxiety, slowed metabolism and decreased heart rate, memory impairment, enlarged tongue, deep voice, swollen neck, PMS, weight gain, hypoglycemia, and high cholesterol and triglycerides. Yet, more than half of all people with thyroid disease are unaware of their condition.

T4 (thyroxine) is an inactive form of thyroid hormone that is converted in the body to T3 (triiodothyronine), the active form. Some hypothyroid patients remain symptomatic on T4 therapy and T3 may also be require for optimal thyroid replacement therapy. However, the only commercially available form of T3 is synthetic liothyronine sodium in an immediate release formulation which is rapidly absorbed and may potentially cause serious side effects including heart palpitations.

Research indicates that to avoid adverse effects, patients and their physicians may wish to consider the use of sustained-release T3 in the treatment of hypothroidism, particularly when the response to levothyroxine (T4) has not been complete. Another option is using a physiologic blend of T4/T3.

J Endocrinol Invest 2002 Feb;25(2):106-9
N Engl J Med 1999 Feb 11;340(6):424-9