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.
The killing occurs during the course of a dangerous felony. This crime is often known as felony murder. A felon can be guilty of murder if a death occurs during the course of a dangerous felony, even if the felon is not the killer. In most states, the death must be a foreseeable result of the initial felony.