Endocrine Abstracts

Introduction: The lipid metabolism is significantly influenced by thyroid hormones. It is well established that overt hypothyroidism (OH) is linked to elevated lipids; however, there is ongoing debate over its impact on subclinical hypothyroidism (SH). The aim of the study was to evaluate the association between serum lipid levels and hypothyroidism and to assess the effect of levothyroxine treatment on lipid profile.

Methods: Parametric data were tested by one way ANOVA and non-parametric data – by Kruskal Wallis test. Effect of treatment was assessed by paired t-test or Wilcoxon signed Rank test.

Results: 65 patients (35 with OH, 30 with SH, and 64 healthy controls were included in the study. Total cholesterol (TC), low density lipoproteins (LDL), high density lipoproteins (HDL) were measured at baseline visit, and after 2 and 4 months of levothyroxine therapy. TC was significantly increased in OH (P < 0.001), but not SH (P = 0.685) at baseline as compared to controls. TC significantly decreased in OH (6.9±2.5 mmol/l at baseline visit, and 5.3±1.5 after 4 months of treatment, P < 0.001), but did not decrease in SH (5.1±1.0 mmol/l at baseline visit, 5.0±1.0 mmol/l after 4 months of treatment). Mean TC in the control group was 5.5±1.0 mmol/l. HDL significantly decreased in OH after 2 months of treatment (1.6±0.6 mmol/l and 1.3±0.3 mmol/l respectively, P < 0.001), but not in SH. OH also showed a significant difference in LDL before and after 4 months of treatment (4.6±2 mmol/l and 3.4±1.1 mmol/l respectively, P = 0.001). TSH and FT4 had a weak positive correlation with TC and LDL, but not HDL.

Conclusion: Our results indicate that compared to the general population, those with overt hypothyroidism, but not subclinical hypothyroidism, have greater levels of LDL and TC. There was a weak correlation found between lipids and FT4 and TSH.