PhD defence M.T. (Merel) Stegenga

Below is a brief summary of the dissertation: 

The thyroid produces T3 and T4, which regulate growth and metabolism in all organs. Excess thyroid hormone leads to weight loss, increased pulse, and restlessness; deficiency causes weight gain, fatigue, and depression. (Malignant) thyroid nodules may also occur. There are three types of thyroid cancer: papillary (PTC), follicular (FTC), and oncocytic (OTC). Treatment includes surgery, radioactive iodine (RAI), and follow-up with ultrasound and tumor markers. Section 2.1 concludes that the latest TNM classification predicts prognosis in PTC and FTC more accurately than the previous version. Section 2.2 shows that 10-year mortality risk increases with age and differs between PTC and FTC, underlining the need to revise TNM. Section 2.3 demonstrates that the new pathological classification better distinguishes low-, intermediate-, and high-risk patients in FTC and OTC. Section 2.4 highlights that recurrence risk in high-risk patients is higher than previously expected. Section 2.5 shows that ATA risk stratification effectively predicts persistent disease and recurrence in patients with metastases. In 3.1, RAI guideline indications are compared by the percentage of missed metastases if RAI were omitted. Less strict guidelines missed 1.3–4.0% of metastases; the strictest guideline missed none but resulted in more (possibly unnecessary) RAI treatments. Sometimes RAI is no longer effective, known as RAI-refractory disease. Section 3.2 shows that in FTC, tumor characteristics are the main risk factors for RAI-refractoriness, while in OTC, metastases play the key role. Chapter 4 outlines the T3-4-Hypo Trial, a randomized study investigating the benefit of adding T3 to T4 in hypothyroidism with persistent fatigue.