BACKGROUND
A thyroidectomy is performed to treat conditions such as thyroid cancer, goiter and hyperthyroidism. After surgery, patients must take thyroid hormone pills (levothyroxine) daily for the rest of their lives. While levothyroxine only needs to be taken once a day, finding the correct dose of this medicine can be challenging. The initial dose of levothyroxine can be determined byt taking into account the patient’s weight, age, sex and other medical conditions. Then serum thyrotropin (TSH) is monitored every 6 to 8 weeks, and the dose is adjusted in small increments to reach the desired TSH level. However, to ensure the medication and TSH have reached a steady equilibrium, the clinician must wait at least 6 weeks after a TSH check before the dose can be adjusted again. Consequently, it can take more than a year to reach a patient’s TSH goal following thyroidectomy, during which patients may experience symptoms of hypothyroidism or hyperthyroidism.

In this study, the authors examined whether using a computerized decision aid tool (DAT) to adjust the levothyroxine dose after only two weeks would be possible. The goal of the present study was to test whether application of the DAT led to more efficient dosage adjustments for patients starting levothyroxine therapy after total thyroidectomy, as compared with the usual dosage adjustments.

THE FULL ARTICLE TITLE
Brun VH et al. Patient tailored levothyroxine dosage with pharmacokinetic/pharmacodynamic modeling: A novel approach after total thyroidectomy. Thyroid. Epub 2021 May 12

SUMMARY OF THE STUDY
This was a trial using a computerized decision aid (DAT) to help doctors adjust levothyroxine dose after thyroidectomy. A total of 135 adults admitted for thyroidectomy to treat toxic or nontoxic goiter, thyroid cancer or Graves’ hyperthyroidism participated in the study. After surgery, all participants were started on levothyroxine at a dose picked by their doctor.

Subjects were then randomly assigned to receive the DAT or usual care. TSH and Free T₄ hormone levels were evaluated 2 weeks after surgery and again 5-6 weeks later. At each time point, the doctor was able to adjust the dose of levothyroxine. In the decision aid tool group, the doctor was assisted by the tool with a graphical plot that provided a recommended dosage change; however, for those in the control group, the doctor was given the lab results only. Participation in the study was stopped once the TSH target was reached. If the TSH target was not reached, participants had follow-up every 6 weeks until the TSH target was reached. The main result measured at the end of the study (called the primary endpoint) was the number of participants who reached their TSH target within 8 weeks after thyroidectomy.

Overall, 35% of patients in the decision aid tool group reached their TSH target by 8 weeks after surgery, as compared with only 15% in the control group (P= 0.006). Among the subgroups, 40% of patients with nontoxic goiters and 59% of patients with thyroid cancer in the decision aid tool group achieved the primary endpoint, as compared with 0% and 19% in the control group, respectively. Using the DAT shortened the average time to reach target TSH by 58 days in the goiter group and 40 days in the cancer group. However, the DAT was not helpful for patients with thyrotoxicosis from Grave’s disease or toxic goiter.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
This study shows that rather than waiting six to eight weeks for hormone levels to stabilize, the clinician can adjust the dose of levothyroxine after only two weeks when assisted by a computerized clinical decision support tool. While it is unclear whether reaching the TSH goal sooner will have a clinically significant impact, this data provides a good foundation for future research in the management of hypothyroidism and moves beyond simple weight-based dosing of thyroid replacement.

— Philip Segal, MD

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