Optimizing Levothyroxine replacement in primary care practice

Abstract

Individuals with hypothyroidism will require lifelong thyroxine replacement therapy to alleviate symptoms and prevent long-term consequences. Levothyroxine (LT4), a synthetic form of thyroxine (T4), is the standard and most prescribed medication for managing hypothyroidism. Triiodothyronine (T3) is another thyroid hormone that can be used in replacement therapy, but it is not typically used as a first-line treatment. However, a combination of T4 and T3 may be considered in uncommon situations when T4 to T3 conversions are reduced. Optimal replacement therapy is individualized, and factors such as age, weight, etiology, comorbidities, and medication interactions must be considered while determining LT4 dose. In addition, individuals on LT4 replacement therapy (TRT) require regular monitoring with thyroid function tests (TFT) and dose adjustments to maintain optimal thyroid function. Individualizing LT4 dosing based on specific factors such as age, weight, comorbidities, and concomitant medications is crucial to achieving optimal thyroid hormone levels and improving patient outcomes. The chapter also explores potential factors that can interfere with LT4 absorption and metabolism, including gastrointestinal conditions, dietary supplements, and drug interactions. Various LT4 formulations are discussed, highlighting differences in bioavailability and their impact on treatment efficacy.