Decision aid tool improves levothyroxine dosing after thyroidectomy
Use of a decision aid tool along with free thyroxine and thyroid-stimulating hormone levels after thyroidectomy may help patients reach a proper dosage of levothyroxine replacement therapy faster, researchers reported in Thyroid.
In data from a randomized controlled trial, providers using a decision aid tool to adjust levothyroxine dosage after thyroidectomy helped patients reach their individual TSH target quicker if they were diagnosed with a nontoxic goiter or cancer, but not with thyrotoxicosis.
“By help of a mathematical model, it is possible to speed up dosage adjustment of levothyroxine after thyroidectomy,” Vegard Heimly Brun, MD, PhD, consultant endocrine surgeon at the University Hospital of North Norway, told Healio. “The method relies on blood samples from the first two weeks after initiation of the medication, before steady state is reached. Months of dosage adjustment can thus be avoided for many patients after thyroidectomy.”
Brun and colleagues developed a decision aid tool algorithm to calculate levothyroxine dosage based on four consecutive free T4 and TSH measurements. To validate the tool, 135 adults who underwent thyroidectomy after a nontoxic goiter, malignant Graves’ disease or toxic multinodular goiter diagnosis were recruited from three hospitals in Norway and Sweden to participate in a randomized controlled trial. After surgery, participants were prescribed a levothyroxine dose based on diagnosis, body weight, age and comorbidity. Participants were randomly assigned to a group in which their provider used the decision-making tool (n = 68) or a control cohort in which free T4 and TSH measurements were available but the tool was not used (n = 67). Participants received a follow-up call 2 to 3 weeks after surgery with an updated levothyroxine dose. At 8 weeks, participants left the study if they reached their individual TSH target. Remaining participants continued follow-up at 6-week intervals until the TSH target was reached.
The decision aid tool group had more participants reach their TSH target 8 weeks after surgery compared with the control group (35% vs. 15%; P = .006). Of patients who had thyroidectomy for goiter, 40% reached their TSH target at 8 weeks with the decision aid tool compared with none of the control group (P = .005). Patients who had thyroidectomy after cancer were also more likely to reach their TSH target after 8 weeks with the decision aid tool compared with controls (59% vs. 19%; P = .003). Those with a goiter or cancer reached their TSH targets in significantly fewer days with the decision aid tool compared with controls.
For patients who had a thyroidectomy due to thyrotoxicosis, individual free T4 could not be estimated due to TSH suppression. In this subgroup, the number who reached their TSH target at 8 weeks was not different between the decision aid tool and control groups, and the decision aid tool group took longer than the control group to reach their TSH target (182 days vs. 115 days; P = .005).
“The failure of the simplified decision aid tool to improve dosage for thyrotoxic patients suggests that individual free T4 and TSH estimations are necessary to achieve successful dosage with our model,” the researchers wrote. “The majority of the patients in the thyrotoxicosis group had a totally suppressed TSH before surgery and were still on antithyroid hormone drugs. Slow recovery of normal TSH dynamics after prolonged suppression made our model vulnerable to mistakes, as it relied heavily on initial blood samples.”
Brun said the decision aid tool works only for patients with healthy TSH or T4 dynamics and no tool is available yet for people with hyperthyroidism and suppressed TSH.
“We also need to do more research on the possible health benefits of faster dosage adjustments,” Brun said. “We know that many patients struggle during the time of suboptimal dosage, but a study to evaluate the consequences needs to be performed.”
For more information:
Vegard Heimly Brun, MD, PhD, can be reached at vegardbrun@gmail.com.
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