Impact of Thyroid Hormones on Human Glucose and Energy Metabolism

This research project aims to clarify the role of changes in thyroid hormone levels in glucose and liver metabolism.

Thyroid hormones regulate endogenous glucose production, insulin sensitivity, lipid metabolism, and lipid storage in the liver. They also appear to enhance insulin sensitivity in other tissues. Furthermore, thyroid hormones stimulate lipolysis and reduce total and LDL-cholesterol levels. The impact of thyroid hormones on insulin secretion is controversial, with some trials demonstrating increased secretion and others showing decreased secretion. Most of this evidence is derived from animal trials, and prospective human trials are lacking.

Clinical scenarios where thyroid hormone levels are altered through therapeutic interventions will be used. In patients with Graves' disease, hyperthyroidism is pharmacologically reduced, whereas in patients with thyroid carcinoma, hyperthyroidism is pharmacologically induced. Before the start of treatment, two weeks and three months after start of treatment oral glucose tolerance tests will be performed for metabolic characterization. Using this approach, differences in glycemic, insulin sensitivity, insulin secretion, lipids, resting energy expenditure, respiratory quotient, hepatic steatosis, eating and exercise behavior will be assessed.

Inclusion criteria

• patients with initial diagnosis of graves disease OR
• patients with initial diagnosis of thyroid carcinoma

Exclusion criteria

• contraindications for oral glucose tolerance test
• Diabetes mellitus
• Fasting glucose level ≥ 200 mg/dL
• Exogenous insulin administration with action at the time of the test
• Current disease with activation of stress hormones
• Post-aggressive metabolism
• Acute infectious disease