Replacement Thyrox doseage shift?

When TSH level is lower that means that your thyroid hormone levels are higher or in more normal ranges, so, you won't need higher doses of supplementary thyroxine.

When you gonna be performed thyroidectomy?

I'm at 150MCG right now. Soon, I'll be taking 75MCG. A radical drop from what I've been on for years. I'm still not sure why the big change but we'll see if the doc knows what he's doing.

Thyroidectomy was in 1996 or so.

You told me the level of TSH but you didn't tell me the level of thyroxine (T4). What is your current level of T4?

Doc didn't have the T4 numbers. He said that the most sensitive is the TSH and that's what they use.
I'll give him a chance, he's dropping me to 100MCG for 6 weeks.

Each laboratory has its own referent values for TSH. What are the referent values for TSH in the laboratory where your TSH was measured?
It is true that TSH-level is the most important parameter for therapy evaluation but for longterm treatment both hormones, TSH and free thyroxine (fT4), should be evaluated. If you had complete thyroidectomy you should take thyroxine substitution for life. Beside TSH and fT4, health condition (presence/absence of symptoms) should be also considered when determining the proper thyroxine dose. You need to take the new dosage of thyroxine at least 8 weeks until you make a new evaluation of the therapy.
You can consult some endocrinologist about this.

I'm not sure what their reference is but I remember starting at 100MCG but I still felt "off". I was on one side of "their" range so I asked to be bumped to 125MCG to see if I improved. I felt much better.
The only reason I was on 150MCG is because the mfg changed and they had a lower potency.
I just picked up my 100MCG prescription last night. Let's see what happens.

Yes. Let us see what will happen.