May 6th, 2011 by DoctorZaidi
The Old Approach to Treat Hypothyroidism?
Most physicians use only T4 (Levothyroxine, L. thyroxine, Synthroid, Levoxyl or Levothroid) to treat an under-active thyroid state, which is also called Hypothyroidism. Why? Because that’s what they have been told to do.
The rationale given for this old, sub-optimal treatment is that some of this T4 gets converted into T3 inside the body. However, a large number of patients continue to have symptoms of hypothyroidism despite taking their T4 medicine. This old approach comes from the era when a blood test for T3 was not widely available.
What is the Optimal Treatment of Hypothyroidism?
A normal thyroid gland produces two types of thyroid hormones, Levothyroxine (or T4) and triiodothyronine (or T3). Then, some of T4 gets converted into T3.
Over the last 10-15 years, some endocrinologists, including myself, started to include T3 level in our patients, in addition to T4 and TSH. We were amazed to find that many patients are relatively low in T3 when they receive T4 alone as their thyroid replacement. Therefore, it is plausible to conclude that conversion from T4 to T3 varies from patient to patient and does not take place as efficiently as was presumed in the past.
Therefore, the most scientific and physiological approach is to give both T4 and T3 to a hypothyroid patient. Check T4 as well as T3 in addition to TSH levels in the blood in order to monitor the adequacy of thyroid hormone replacement.
T3 is also known as liothyronine.
Drugs to Treat Hypothyroidism
Brand name Generic Name
Armour Thyroid Levothyroxine (T4) + Triiodothyronine (T3)
Synthroid Levothyroxine (T4)
Levoxyl Levothyroxine (T4)
Cytomel Liothyronine (T3)