I just found out that a history of thyroid deficiency runs thru my family. I will begin getting tests done soon but doctors usually don't know much about how their therapies/drugs effect bodybuilding. What are the effects/pro's/con's of taking a thyroid replacement drug? Added work? Eating changes? Inhibited growth?

Under active thyroid can have a ton of negative effects on the body. Not the least of which are excessive fat, lack of energy, decreased mood, etc.

In body building t-3 is the drug of choice, and t-4 is rarely used.

T-3 is generally used to lose fat in precontest stages once one has already reached the lowest possible fat with diet and exercise alone. Most often it is used in a pyramid fashion starting with 25mcg per days and working up slowly to 100mcg and then tapering back off to prevent crashing. The entire cycle is usually kept to 6 weeks or less.

Lately many have found that low doses of t-3 (12.5mcg eod) also work well with bulking cycles because they increase cellular activity.

This drug is not for novices and can catabolize muscle more quickly than anything else that I know of.