Alterations in Free Fatty Acid Metabolism in Endocrine Disorders. Part I: Effect of Thyroid Hormone

Fasting levels of plasma free fatty acid (FFA) and the response to epinephrine and norepinephrine infusions have been measured in normal subjects. The results have been compared with those of studies done on patients with hyperthyroidism, hypothyroidism and panhypopituitarism. In hyperthyroidism there was a significant elevation of resting levels of FFA and an enhanced mobilization of FFA after catechol amine stimulation. Hypothyroid subjects presented a wide variation in fasting levels and a broad range of response to catechol amine stimulation. Mobilization of FFA after catechol amine infusion was decreased, and this diminished response appeared to be related to the degree of thyroid deficiency. Preliminary observations on the disappearance rates of labeled palmitic acid suggested that thyroid hormone has an effect on utilization as well as mobilization of fatty acids. Studies in panhypopituitary patients indicate that fasting levels and the response to catechol amines are related primarily to thyroid d...