Got it. Thanks a lot for the explanation.Too high metabolism may lead to muscle catabolism if calorie intake is insufficient. T3 is "known" as catabolic hormone in medicine mostly because some studies used very high doses without matching increase in calories and weight/muscle loss was seen. Progesterone suffers from the same misconceptions. Many people use progesterone and do not increase calories, leading to net loss in weight and sometimes muscle mass. That's the context in which I made that statement.