The best way to compare meds is to convert to equivalent T4 amounts. The 88 mcg of Synthroid plus 15 mcg of Cytomel is equivalent to 133 ,cg pf T4. Since T3 is 3 times as potent as T4 it is calculated as follows: 88 plus (3 times 15) equals 133. Since a grain of Armour contains 39 mcg of T4 and 9 mcg of T3, that is equal to 66 mcg of T4. So 2 grains of Armour is equivalent to only 132 mcg of T4.
Overall you went from 88+ 15 to 78 plus 18, so no noticeable effect would be expected from the change.
What are your most recent thyroid related test results and reference ranges shown on the lab report? What symptoms do you have?
The correct definition for hypothyroidism is not just "inadequate thyroid hormone" but instead, it is "insufficient T3 effect in tissue throughout the body due to inadequate supply of, or response to, thyroid hormone". This definition correctly recognizes that TISSUE T3 EFFECT determines your thyroid status and associated symptoms. Since there are no biochemical tests that correlate adequately with TISSUE T3 EFFECT, no biochemical test can be used as pass/fail decisions about your thyroid status. Instead the best available diagnostic is an evaluation for symptoms that occur more frequently with hypothyroidism, When your thyroid levels are adequate for YOUR specific needs, and other variables that affect the response to thyroid hormone are adequate, then hypo symptoms disappear.
A recent, excellent scientific study concluded that: " Hypothyroid symptom relief was associated with both a T4 dose giving TSH-suppression below the lower reference limit and FT3 elevated further into the upper half of its reference range." For many people, in order to achieve adequate Free T3 levels, this requires the addition of T3 to their thyroid med, from a source such as Armour Thyroid, or Cytomel .
So you need further increases to your Armour dosage to achieve the above. If you run into resistance from your doctor, then along with other info you can mention that the average human body produces 100 mcg of T4 and 10 mcg of T3 daily. Using the formula from above this equates to 130 mcg of T4 and thus is equivalent to 2 grains of Armour Thyroid. Since our bodies do not absorb the med 100 % that means that the average daily requirement for thyroid med has to be more than 2 grains. Most people find they need somewhere between 3 and 5 grains of Armour for symptom relief.
In addition the response to thyroid hormone is affected by a number of variables. Some of the major variables are Vitamin D, B12 ferritin and cortisol. Cortisol needs to be neither too low or too high. Vitamin D should be at least 50 ng/mL. B12 in the upper part of its range, and ferritin should be at least 100. So if not tested for those you should do so and then supplement as needed to optimize.
If you want to confirm any of this please click on my name and then scroll down to my Journal and read at least the one page overview of a full paper on Diagnosis and Treatment of Hypothyroidism: A Patient's Perspective.