Once we decide to treat a patient with laboratory findings and a clinical presentation compatible with hypothyroidism, how do we initiate treatment with synthetic LT4? How do we monitor with respect to LT4, T3, TSH, and their global health?
When the decision of treating patients is taken, the next step is what type of formulation and how to titrate the dose. The, um, All of the guidelines and in particular the American Thyroid Association uh guidelines uh uh recommend the use of levothyroxine. This is a very rational approach because levothyroxine is well studied. It has multiple formulations and it's easily tightrable and on top of that, it's relatively cheap. Um, and most important from the patient's perspective can be taken on a once a day administration. Um Again, uh, my, uh, go to approach is telling patients to take, uh, levothyroxine first thing in the morning. Avoid interference with other drugs or supplements, and waiting at least 30 minutes before having breakfast. This approach is very robust. And the next step is when to titrate. The goal is If we are dealing with hypothyroidism and we are not talking at this time in treatment of thyroid cancer, the treatment goal is achieving a normalization of. And for the vast majority of cases that will result in a normalization of free T4 and total T3. Very seldom at this time and age, uh, uh, patients with hypothyroidism present with significant derangement uh of uh thyroid hormone levels. Again, the diagnosis is mostly done uh on uh TSH abnormalities. Florida hypothyroidism is uh not as common as it used to be in terms of uh a percentage of patients who are treated for hypothyroidism. Levothyroxine or T4 has an extremely long half-life, 7 days, and that allows first of all an administration every day on a daily basis, but at the same token requires patience in expecting improvements in symptoms and also not jumping the gun and making too quick or too frequent adjustments. So, um, the rule is waiting at least 56 half-lives of the medication in order to achieve a steady state. And, uh, uh, so we want to wait for at least 6 weeks before making an adjustment by measuring TSH. Usually, the dosing is weight-based and we've proven that a patient without endogenous thyroid hormone production will require 1.6 mcg per kg of levothyroxine. And that there are quite significant interindividual variabilities, but that, that would be a good start point for a full replacement of thyroid hormone. In the scope of uh subclinical hypothyroidism, uh, we can definitely start on a much lower dose. Um, counting on the fact that uh uh the um intrinsic feedback of the thyroid axis will allow for uh a different uh uh different doses. And again, the expectation is that in 6 weeks, we should have a normalization of TSH.
