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INTRODUCTION: Levothyroxine (L-T4) monotherapy is the standard of care for the treatment of hypothyroidism. A minority of the L-T4-treated patients remain symptomatic and report better outcomes with combination therapy that contains liothyronine (L-T3) or with desiccated thyroid extract (DTE). GOAL: To assess patient preferences in the treatment of hypothyroidism. METHODS: A systematic review, meta-analysis, meta-regression, and network meta-analysis (NMA) of randomized controlled trials (RCTs) comparing treatments for adults with hypothyroidism (L-T4 vs. L-T4+L-T3 or DTE). Searches were conducted in PubMed, Embase, and Cochrane databases up to April 10, 2024. Data extraction and quality assessment were independently performed by four researchers. RESULTS: Eleven RCTs (eight cross-over studies) with a total of 1,135 patients were considered. Overall, 24% of patients preferred L-T4 versus 52 % who preferred L-T4+L-T3 or DTE; 24% had no preference. The meta-analysis confirmed the preference for combination therapy over L-T4 monotherapy (RR: 2.20, 95% CI: 1.38 to 3.52; p = 0.0009). Excluding four studies reduced the high heterogeneity (I2 = 81%) without affecting the results (RR: 1.97, 95% CI: 1.52 to 2.54; p < 0.00001; I2 = 24%). This preference profile remained when only crossover studies were considered (RR: 2.84, 95% CI: 1.50 to 5.39; p < 0.00001). Network meta-analysis confirmed the preference for DTE and L-T3+L-T4 versus L-T4 alone. CONCLUSION: Patients with hypothyroidism prefer combination therapy (L-T3+L-T4 or DTE) over L-T4 monotherapy. The strength of these findings justifies considering patient preferences in the setting of shared decision-making in the treatment of hypothyroidism.
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CONTEXT: Thyroid-stimulating hormone (TSH) trajectory classification represents a novel approach to defining the adequacy of levothyroxine (LT4) treatment for hypothyroidism over time. OBJECTIVE: This is a proof of principle study that uses longitudinal clinical data, including thyroid hormone levels from a large prospective study to define classes of TSH trajectories and examine changes in cardiovascular (CV) health markers over the study period. METHODS: Growth mixture modeling (GMM), including latent class growth analysis (LCGA), was used to classify LT4-treated individuals participating in the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) based on serial TSH levels. Repeated measure analyses were then utilized to assess within-class changes in blood pressure, lipid levels, hemoglobin A1c, and CV-related medication utilization. RESULTS: From the 621 LT4-treated study participants, the best-fit GMM approach identified 4 TSH trajectory classes, as defined by their relationship to the normal TSH range: (1) high-high normal TSH, (2) normal TSH, (3) normal to low TSH, and (4) low to normal TSH. Notably, the average baseline LT4 dose was lowest in the high-high normal TSH group (77.7â µg, P < .001). There were no significant differences in CV health markers between the classes at baseline. At least 1 significant difference in CV markers occurred in all classes, highlighted by the low to normal class, in which total and high-density lipoprotein cholesterol, triglycerides, and A1c all increased significantly (P = .049, P < .001, P < .001, and P = .001, respectively). Utilization of antihypertensive, antihyperlipidemic, and antidiabetes medications increased in all classes. CONCLUSION: GMM/LCGA represents a viable approach to define and examine LT4 treatment by TSH trajectory. More comprehensive datasets should allow for more complex trajectory modeling and analysis of clinical outcome differences between trajectory classes.
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CONTEXT: The effectiveness of levothyroxine (LT4) in restoring thyroid hormone (TH) homeostasis, particularly serum thyroxine (T4) and triiodothyronine (T3) levels, remains debatable. OBJECTIVE: This work aimed to assess TH homeostasis in LT4-treated individuals using data from the Longitudinal Study of Adult Health in Brazil (ELSA-Brasil) study. METHODS: The ELSA-Brasil study follows 15 105 adult Brazilians (aged 35-74 years) over 8.2 years (2008-2019) with 3 observation points assessing health parameters including serum thyrotropin (TSH), free T4 (FT4), and free T3 (FT3) levels. We analyzed 186 participants that initiated treatment with LT4 during the study, and 243 individuals continuously treated with LT4 therapy. RESULTS: Initiation of therapy with LT4 resulted in an 11% to 19% decrease in TSH, an approximately 19% increase in FT4, and a 7% reduction in FT3 serum levels (FT3 dropped >10% in â¼40% of the LT4-treated patients). This was associated with an increase in triglyceride levels and utilization of hypolipidemic and antidiabetic medications. Participants continuously treated with LT4 exhibited a stable elevation in serum FT4 and a reduction in serum FT3 and TSH levels. While 115 participants (47.3%) had at least 1 serum FT4 levels above the control reference range (>1.52â ng/dL), 38 participants (15.6%) had at least 1 serum FT3 below the reference range (<0.23â ng/dL). CONCLUSION: The present results challenge the dogma that treatment with LT4 for hypothyroidism restores TH homeostasis in all patients. A substantial number of LT4-treated patients exhibit repeated FT4 and FT3 levels outside the normal reference range, despite normal TSH levels. Further studies are needed to define the clinical implications of these findings.