Why Don’t I Feel “Right” on My Thyroid Hormone Replacement Therapy?

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Why Don’t I Feel “Right” on My Thyroid Hormone Replacement Therapy?

By: Jim PaolettiRPh, FAARFM, FIACP 

For thyroid hormone replacement therapy, the standard of practice for thyroid testing is measuring Thyroid Stimulating Hormone (TSH) alone or in combination with measuring T4. Unfortunately, these levels do not reflect the peripheral conversion of free T4 to the much more active free T3. The thyroid gland produces T4 that travels to various tissues throughout the body. T4 then converts into the active T3 hormone. A normal amount of T4 will not produce a normal amount of T3 when the conversion process gets blocked. As a result, thyroid function can be low even with “normal” TSH and T4 levels.


About thyroid hormone replacement therapy


The standard of practice in thyroid replacement is to give the patient Synthroid® (levothyroxine or T4). If the patient’s system can’t convert T4 to T3 optimally, he produces more reverse T3 that blocks T3 from working. Using T4 alone for thyroid replacement therapy does not take into consideration whether the individual patient is converting T4 to T3 efficiently.

Some patients respond better using a combination of T4 and T3 in their therapy. Products made from USP Desiccated Porcine Thyroid contain both T4 and T3. Armour Thyroid®, NP Thyroid®, Nature-Throid®, and WP Thyroid® are examples of desiccated porcine thyroid. These preparations contain a 4:1 T4 to T3 ratio. These products are often referred to as “natural” thyroid replacement products since they consist of a pig’s thyroid gland. These substances may be “natural” to pigs but are not automatically “natural” to humans.

Thyrolar® is another product that contains T4 and T3 in the same 4:1 ratio. The normal ratio in humans is about 3.3 to 1. Thus, these products provide more T4 to T3 ratio than humans normally produce.  


Individualized treatment


To eliminate the problem of providing only T4 or giving too much T4 to patients that do not convert T4 efficiently to T3, doctors prescribe a combination of 2 separate products—one containing T4 and one containing T3. However, manufactured products containing only T3 come in limited strengths. Studies have shown that the proper dosing of T3 immediate-release products is 3 times a day. Yet even at the lowest strength of commercially manufactured T3, a half tablet given 3 times a day could be more than many patients need.

Compounding pharmacists can provide the right thyroid hormones in the right amount for each patient. Compounded thyroid preparations can contain T4, T3, or a combination of both according to the patient’s prescription. Also, the amounts of each hormone can be formulated based on the patient’s testing levels and clinical response. Compounding pharmacies use bio-identical T4 and T3. These pure powders are identical in molecular structure to the hormones produced in the human body.


Advantages of compounded thyroid hormone preparations


Like any compounded mixture, compounded thyroid hormone preparations may eliminate unwanted ingredients like gluten, corn, dyes, etc. Commercially manufactured thyroid products can contain lactose, cornstarch, dextrose and more. Some patients cannot tolerate these ingredients even in minute amounts, yet some product labels do not reflect them.

Compounded thyroid hormone preparations can be made into Immediate Release (IR) or Slow Release (SR) formulas. The real advantage here is with T3 therapy. For better compliance, once a day T3 SR dosing can be given instead of the 3 times a day dosing requirement for T3 IR preparations.


Alternative for thyroid replacement products


Compounding pharmacists are knowledgeable about the nutritional requirements necessary for the proper production, metabolism, and utilization of thyroid hormones. Some patients prefer taking nutritional supplements coupled with lifestyle change instead of taking a thyroid replacement product For such cases, we recommend the supplement Thyroid Support with Zinc. It’s a unique blend of minerals, vitamins, amino acids, and herbal supplements to help support the health of your thyroid. 



  • May increase energy 
  • May improve metabolic rate 
  • Zinc and selenium – encourage conversion of T4 (inactive) to T3 (active) 
  • L-Tyrosine – serves as a precursor for thyroid hormone 


If you are experiencing symptoms of low thyroid, click here to have a 15minute discovery call with our consultant pharmacist.