We know that 'lack of Synthroid' is NOT the cause of any thyroid problem. Exposure to chemicals, e.g. perchlorate, common food intolerances (e.g. wheat/dairy), adrenal fatigue and nutrient deficiencies are the cause of 'hypothyroidism' in the vast majority of cases.
An F3 felony is a shorthand expression for a class or category 3 (or III) felony in jurisdictions that use numbered offense categories. What such an offense is punishable by and whether it is punishable by more or less than an F2 felony depends completely on the laws of the jurisdiction in question.
Felonies are the most serious type of criminal offense. Felonies often involve serious physical harm (or threat of harm) to victims, but they also include offenses like white collar crimes and fraud schemes. Offenses that otherwise are misdemeanors can be elevated to felonies for second-time offenders.