T4 is the less active form of thyroid hormone. Medications like Levothyroxine and Synthroid are forms of T4.
T3 is the more active form of thyroid hormone. Medicatons like Cytomel are T3.
T4 is converted into T3 primarily in the liver, but also in the kidneys. The co-factors for converting T4 to T3 include the nutrient selenium and iron.
Hypothyroidism is usually treated with thyroid hormone replacement. Optiions include:
T4=Synthroid, Levothyroxine
T3=Cytomel
Combination T4/T3= Armour, Nature-Throid
My Work With Thyroid Patients
I work with many patients who already have a diagnosis of hypothyroidism but feel that there is still a need to fine-tune or optimize their treatment. Here are some examples.
I'm already on Synthroid or Levothyroxine and my TSH values are in the "normal range," but I still feel tired, cold and bloated.
If a patient's TSH is "high normal," the medication dosage may be inadequate. In this case, I will work with patients to get their TSH in the optimum range by adjusting the dose.
If the patient is taking only T4 (Synthroid or Levothyroxine or generic version), they may do better with the addition of T3. This can be with something like Armour or the addition of prescription Cytomel. I counsel patients on which option may be most appropriate in their situation. Doing an expanded thyroid lab may be helpful in determining the best course of action.
I'm taking thyroid hormone replacement already, and my TSH is in the optimal range. I seem to have energy in morning, but by late afternoon I feel very tired--as if I have hypothyroidism in the late afternoon only.
If the labs are optimal and the meds are supposedly optimal, I might recommend a time-release form of the thyroid medication. I use a compounding pharmacy to prescribe a time-release formulation so that the thyroid hormone is made available throughout the day, instead of having a peak in the morning and then tapering off towards the afternoon.
I would also look into other factors such as diet (for example, eating too many carbs or sugars for lunch can make one sleepy in the afternoon).
I would consider if the patient may have "adrenal fatigue" and treat this appropriately.
I am on T4 (Synthroid or Levothyroxine), but most of my symptoms seem to revolve around mental symptoms such as poor memory and lethargy.
Poor memory and lethary are two symptoms which may support the addition of T3 horrmone (Armour or Cytomel). This is supported by a study published in the New England Journal of Medicine.
