Here are the steps that could get your arrested for a debt lawsuit in Virginia. The first paper you get is a warrant in debt. Warrant makes it sound worse than it is. (And just ignoring court papers is never a good idea.) The warrant in debt cannot get you arrested.
According to the conversion chart, 1 grain (60 mg) is equal to 100 mcg snythroid, and 90 mg Armour is equal to 150 mcg levo. According to the manufacturer, there is 38 mcg of T4 and 9 mcg T3 in each grain. So if you work it out that way, 90 mg has only 57 mcg of T4 and 13.5 mcg T3.
By actual weight, it is not the same. 100 grains measured by volume of Goex FFg is about 101.3 grains by weight. 100 grains measured by volume of Pyrodex RS is about 72.5 grains by weight. Pyrodex is where confusion can start to set in, as the standard F designations of powder coarseness start to go out the window.