1. 1. This experiment was carried out to study the effects of thyroidectomy or treatment with an anti-thyroid drug (Methimazole) on the lipolytic and glycogenolytic responses to fasting, noradrenaline and glucose tolerance test in young growing pigs. 2. 2. Male and female crossbred pigs weighing 15–30 kg were used. 3. 3. Fasting caused a slight hypoglycemic response but without statistical differences between euthyroid and thyroid-deficient animals. 4. 4. Free-fatty acids mobilization was significantly different between euthyroid and thyroid-deficient pigs and, the lipolytic effect of NA was lower in thyroidectomized animals than in treated or euthyroid pigs. 5. 5. Glucose tolerance test was not different among the groups. However, FFA mobilization during the GTT was significantly different. 6. 6. The results suggest that the interaction between catecholamines-thyroid hormones play an important role in the FFA mobilization in vivo.