Levothyroxine is the most used thyroid hormone replacement when the thyroid gland is failing. Because dosage adjustment normally takes several months, the investigators have developed a decision support tool (DST) that predicts optimal dosage based on repeated blood samples the first 2 weeks after initiation of therapy. In this randomized study the investigators will include patients that start levothyroxine therapy after total thyroidectomy. The use of DST to advice the physician about an early dosage adjustment will be compared with common clinical practice, that is dosage adjustment every 2 months. The effect of DST use will be assessed by studying the possible relationship between fast optimal dose adjustment, patient reported outcome measures, and ability to work.