General comments on tissue sensitivity to thyroid hormones in starvation.

The interrelationship between thyroid hormones and catecholamines is discussed. It is known that hypothyroidism will decrease tissue sensitivity to exogenous catecholamines. There is, however, no experimental proof that the thyroid hormones changes, particularly the low serum T(3) levels encountered in systemic illness and starvation, are sufficient to change tissue sensitivity to catecholamines. Catecholamines and thyroid hormones influence thermogenesis. Recently a decreased effectiveness of thyroid hormones in the starving hypothyroid rat has been documented. It has, however, not been excluded that part of this change is due to a combined change in effectiveness of thyroid hormones and catecholamines on thermogenesis.