What is meant by the calorigenic effect of thyroid hormones?

Actually its the sheer capacity to gradully increase the basal metabolicr rate or the BMR, this happens when thyroid harmones get increased in the bodys heat production along with tissues oxygen consumption, and also the results tells that the calorigenic effect of GH is not mediated only through increased conversion of T4 to T3 thyroid harmones

Calorigenic effect entails generation of metabolic heat. Thyroid hormones have calorigenic (thermogenic) effect which generate heat and may be related to psychological response to cold. There are two most important thyroid hormones T4 and T3. They accelerate glucose metabolism which increases heat production, basal metabolic rate and oxygen consumption. Under certain conditions T3 hormone can also uncouple oxidative phosphorylation resulting to decreased ATP production and increasing heat liberated / mole of glucose