Characteristics of Dyslipidemia in Adults With Resistance to Thyroid Hormone β.

Objective: To assess determinants of dyslipidemia (specifically raised serum low-density lipoprotein cholesterol and triglycerides, and reduced high-density lipoprotein cholesterol) in individuals with Resistance to Thyroid Hormone β (RTHβ).

Methods: Multivariable linear regression analyses of cross-sectional fasting serum lipid profiles from 105 genetically-confirmed individuals with RTHβ (mean age 40.0 years, 40% males) were conducted, including candidate variables with plausible independent associations with the individual components of dyslipidemia such as indices of thyroid function, plasma non-esterified fatty acid concentrations, and insulin resistance assessed using the Homoeostasis Model Assessment equation.

Results: Age was positively related to both serum total and low-density lipoprotein-cholesterol concentrations (P < .001), while there were similar directional associations between body mass index and total:high-density lipoprotein-cholesterol ratio, and Homoeostasis Model Assessment-insulin resistance and serum triglycerides (P ≤ .007). Plasma non-esterified fatty acid concentrations were not associated with serum triglycerides. The only thyroid function measure revealed by the individual models was an inverse association between reverse triiodothyronine and serum triglycerides (P = .009).

Conclusions: The dyslipidemia associated with RTHβ shares recognized contributory factors found in studies of the general population but appears independent of thyroid status. The reason for the significant inverse association between circulating reverse triiodothyronine and serum triglyceride concentrations is unclear and merits further investigation.