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Hypothyroidism Contributes to Increased Triglyceride Levels Among Patients with Systemic Sclerosis To the Editor: We read with interest the article by Kodera and colleagues1 on anti-lipoprotein lipase antibody-mediated lipid metabolism abnormalities in patients with systemic sclerosis (SSc). The report provides new insight into the pathogenesis of dyslipidemia in SSc and probably in other connective tissue disorders. The findings are of special importance in light of the increased prevalence of macrovascular disease observed in this group of patients2. However, according to the results obtained in the study, only one-third of patients with increased triglyceride levels had anti-lipoprotein lipase antibody, which suggests the involvement of other factors. A lipid profile is the result of complex metabolic processes involving dietary habits, environmental influences, race, and endocrine system function. Among the latter, thyroid function is of great interest, with its influence on lipoprotein metabolism. We describe our experience in lipid metabolism among patients with diffuse SSc. In a cohort of 49 patients with diffuse SSc we observed clinical and laboratory features of hypothyroidism in 13 patients (27%) and increased triglyceride levels in more than 55%. Unexpectedly, no differences were observed between hypothyroid and euthyroid SSc patients with regard to their total cholesterol or HDL and LDL-cholesterol levels. Moreover, the patients with hypothyroidism had statistically significantly higher levels of triglycerides than euthyroid patients with SSc3. Hypothyroidism is a common finding in patients with SSc. It is estimated that about half of SSc patients experience overt or latent hypothyroidism4. In contrast to previous reports2,5, patients with SSc showed marked lipid metabolism abnormalities, which may predispose them to early development of macrovascular disease and serious cardiovascular complications. SSc has a very strong influence on triglyceride metabolism in all subgroups of patients, since all SSc patients had higher triglyceride levels. Thus, hypothyroidism may partially explain the elevation of triglyceride levels in the patients with SSc. Kodera, et al have provided more information on lipid metabolism in SSc, supporting the effect of autoimmune mediation upon lipoprotein-lipase, a key enzyme in lipid metabolism. Consistent with this finding, hypothyroidism may be responsible for triglyceride elevation in patients who had no anti-lipoprotein lipase autoantibodies. On the other hand, immune-mediated lipoprotein lipase dysfunction could be responsible for increased triglyceride levels in euthyroid patients with SSc. The findings of these 2 studies might offer a way to verify the hypothesis on overlapping anti-lipoprotein lipase antibody and hypothyroidism, and the influence of both conditions on lipid metabolism in patients with SSc. PRZEMYSLAW J. KOTYLA, MD, PhD, Lecturer; MACIEJ LEWICKI, Assistant; EUGENE J. KUCHARZ, MD, PhD, FRCP, Professor of Medicine, Chairman, Department of Internal Medicine and Rheumatology, Medical University of Silesia, Ziolowa 45/47, 40-635 Katowice, Poland. E-mail: pkotyla@slam.katowice.pl REFERENCES 1. Kodera M, Hayakawa I, Komura K, et al. Anti-lipoprotein lipase antibody in systemic sclerosis: Association with elevated serum triglyceride concentrations. J Rheumatol 2005;32:629-36. 2. Ho M, Veale D, Eastmond C, Nuki G, Belch J. Macrovascular disease and systemic sclerosis. Ann Rheum Dis 2000;59:39-43. 3. Gozdzik J, Kotyla PJ, Kucharz EJ, Brzezinska-Wcislo L. Lipid profile in patients with systemic sclerosis [abstract]. Ann Rheum Dis 2001;60 Suppl 60:199. 4. Kucharz EJ. Thyroid disorders in patients with progressive systemic sclerosis: A review. Clin Rheumatol 1993;12:159-61. 5. Bruckdorfer RK, Hillary JB, Bunce T, Vancheeswaran R, Black CM. Increased susceptibility to oxidation of low-density lipoproteins isolated from patients with systemic sclerosis. Arthritis Rheum 1995;38:1060-7. |